Semiconductor integrated circuit and drive apparatus including the same

ABSTRACT

A semiconductor integrated circuit includes a first transmission circuit generating and outputting a first transmission signal reflecting a first data signal supplied from outside, a first reception circuit reproducing the first data signal based on a first reception signal, a first isolation element isolating the first transmission circuit from the first reception circuit and transmitting the first transmission signal as the first reception signal, a second transmission circuit generating and outputting a second transmission signal reflecting a second data signal supplied from outside, a second reception circuit reproducing the second data signal based on a second reception signal, a second isolation element isolating the second transmission circuit from the second reception circuit and transmitting the second transmission signal as the second reception signal, and a third transmission circuit generating and outputting a third transmission signal reflecting the second data signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation Application of U.S. patentapplication Ser. No. 13/535,256 filed on Jun. 27, 2012, which is basedon and claims priority from Japanese Patent Application No. 2011-188245,filed on Aug. 31, 2011, the entire contents of which is incorporatedherein by reference.

BACKGROUND

The present invention relates to a semiconductor integrated circuit anda drive apparatus including the semiconductor integrated circuit. Moreparticularly, the invention relates to a semiconductor integratedcircuit that transmits signals via an isolation element, and to a driveapparatus that includes the semiconductor integrated circuit.

Isolation elements such as the photo-coupler, inductor-coupled isolator,capacitor-coupled isolator, and GMR (Giant Magneto Resistive) elementisolator are currently used as the means for transmitting signalsbetween a plurality of semiconductor chips each operating on a differentsource voltage.

For example, the photo-coupler uses one chip to convert an electricsignal to an optical signal before getting another chip to convert thatoptical signal to an electric signal, thus providing isolation betweentwo semiconductor chips. The inductor-coupled isolator uses one coil toconvert an electric signal to magnetism before getting another coil toconvert the magnetism to an electric signal, thus ensuring isolationbetween two semiconductor chips. The capacitor-coupled isolator uses oneelectrode of a capacitative element to convert an electric signal to anelectric field before utilizing the other electrode of the element toconvert the electric field to an electric signal, thereby providingisolation between two semiconductor chips. The GMR element isolator usesa coil to convert an electric signal to magnetism before utilizing a GMRelement to convert the magnetism to an electric signal, thereby offeringisolation between two semiconductor chips.

The above-described isolation elements are used in today's power controlcircuits such as inverter equipment and converter equipment.Specifically, this type of power control circuit of recent yearsoperating on one power supply system transmits a control signal outputfrom a microcomputer to a chip of another power supply system via anisolation element, thereby converting the voltage level of the controlsignal in question. The power control circuit proceeds to get a gatedriver amplifying the control signal with its voltage level converted,before feeding the amplified control signal to a control terminal of apower transistor (output transistor) that controls currents flowingthrough a load.

Some related art is disclosed in the following literature: JapaneseUnexamined Patent Publication No. 2009-49035 (called the PatentLiterature 1 hereunder), Japanese Unexamined Patent Publication No. Hei9(1997)-312555 (Patent Literature 2), Japanese Unexamined PatentPublication No. 2002-84173 (Patent Literature 3), Japanese UnexaminedPatent Publication No. 2004-222367 (Patent Literature 4), and JapaneseUnexamined Patent Publication No. Hei 5(1993)-29914 (Patent Literature5).

Disclosed in the Patent Literature 1, an intelligent power module for astep up/down converter includes a CPU, an isolation transformer, asafeguard-equipped gate driver IC, and an IGBI (Insulated Gate BipolarTransistor). The CPU generates a gate drive PWM signal designatingconduction or non-conduction of the IGBT, and transmits the signalinsulatingly to the safeguard-equipped gate driver via the isolationtransformer. Based on the gate drive PWM signal, the safeguard-equippedgate driver IC generates a gate signal and feeds it to the controlterminal of the IGBT for a switching operation. The chip on which theIGBT is formed has a temperature sensor and a current sensor.

Upon determining that the current flowing through the IGBT has exceededa threshold value possibly triggering IGBT destruction based on anoverheat detection signal from the temperature sensor and/or on anovercurrent detection signal from the current sensor, thesafeguard-equipped gate driver IC transmits an alarm signal to the CPU.On receiving the alarm signal from the safeguard-equipped gate driverIC, the CPU stops generating the gate drive PWM signal and thereby cutsoff the current flowing through the IGBT.

A switching circuit control apparatus disclosed in the Patent Literature2 includes a mask circuit that masks information signals such as atemperature signal and a current signal only while switching noise isbeing generated from a switching circuit that repeats on and offoperations. The switching circuit control apparatus detects suchinformation signals from inside the switching circuit or from withinelectric circuits adjacent to and affected by the switching circuitgenerating the switching noise. If the switching circuit controlapparatus detects an abnormality in temperature or in other parametersbased on the information signals except during the masking period, theapparatus supplies a gage circuit with a gate control signal such as aswitching stop command or a switching reduction command.

Consequently, the switching circuit control circuit can detect theinformation signals at high speed without making false determination byaverting the adverse effects of the noise from the switching circuit,according to the Patent Literature 2.

The Patent Literature 3 discloses a power semiconductor device thatsecurely protects power transistors against an overcurrent state byunfailingly detecting the generation of that state without making falsedetermination even if noise is detected in a sense voltage obtained byhaving a sense current detected with a sense resistor.

A gate drive apparatus disclosed in the Patent Literature 4 drives amain semiconductor device of a power converter by the gate. The gatedrive apparatus includes a voltage detection part, a waveform controlcircuit, a reference power source, and a voltage comparator. The voltagedetection part is coupled to the collector terminal of the mainsemiconductor device and detects a collector voltage of that device. Thewaveform control circuit is coupled in electrical parallel to thevoltage detection part and controls differentially the collector voltagedetected by the voltage detection part. The reference power sourcegenerates a reference voltage. The voltage comparator compares thereference voltage from the reference power source with the collectorvoltage controlled by the waveform control circuit. Based on the resultof the comparison, the voltage comparator outputs an abnormalitydetection signal.

In this manner, the gate drive apparatus protects the main semiconductordevice from a short circuit or an overcurrent at high speed, accordingto the Patent Literature 4.

An output buffer circuit disclosed in the Patent Literature 5 includesan output buffer, a power source noise detection circuit, and a groundnoise detection circuit. The output buffer has a first and a second PMOStransistor coupled in parallel between a power terminal and an outputterminal OUT and a first and a second NMOS transistor coupled inparallel between a ground terminal and the output terminal OUT.

When the potential of the power terminal drops due to a change in thepotential level of an output signal OUT, the power source noisedetection circuit detects the potential drop and acts to cut off thesecond PMOS transistor during the potential drop period. When thepotential of the ground terminal rises because of a change in thepotential level of the output signal OUT, the ground noise detectioncircuit detects the potential rise and acts to cut off the second NMOStransistor during the potential rise period.

Thus by reducing its drive capability only during the period where thepower source potential or ground potential is being changed, the outputbuffer circuit prevents the other circuits on the same chip frommalfunctioning, according to the Patent Literature 5.

SUMMARY

The configuration disclosed in the Patent Literature 1 is designed todetect the overcurrent flowing through the IGBT and its overheat toprevent IGBT destruction. This configuration is not intended to detectabnormalities that can cause a malfunction in signal transmissionthrough the isolation transformer.

The configuration disclosed in the Patent Literature 2 is designed todetect the information signals such as the temperature signal andcurrent signal inside the switching circuit or within the electriccircuits adjacent to and affected by the switching circuit generatingthe switching noise. This configuration is not intended to detectabnormalities that can cause a malfunction in signal transmissionthrough the isolation element. To begin with, the configurationdiscussed in the Patent Literature 2 has no arrangements forimplementing signal transmission through the isolation element. Thus itis obvious that the configuration does not detect any abnormality thatmay cause malfunctioning in the signal transmission via the isolationelement.

The configuration disclosed in the Patent Literature 3 is designed todetect the overcurrent flowing through the power transistor and notintended to detect abnormalities that can cause a malfunction in signaltransmission through the isolation element. To begin with, theconfiguration discussed in the Patent Literature 3 has no arrangementsfor implementing signal transmission through the isolation element. Thusit is obvious that the configuration does not detect any abnormalitythat may cause malfunctioning in the signal transmission via theisolation element.

The configuration disclosed in the Patent Literature 4 is designed toprotect the main semiconductor device against a short circuit or anovercurrent by detecting the collector voltage of that device. Theconfiguration is not intended to detect abnormalities that can cause amalfunction in signal transmission through the isolation element. Tobegin with, the configuration discussed in the Patent Literature 4 hasno arrangements for implementing signal transmission through theisolation element. Thus it is obvious that the configuration does notdetect any abnormality that may cause malfunctioning in the signaltransmission via the isolation element.

The configuration disclosed in the Patent Literature 5 is designed tocontrol the drive capability of the output buffer by detecting changesin the power potential and ground potential for driving that buffer. Theconfiguration is not intended to detect abnormalities that can cause amalfunction in signal transmission through the isolation element. Tobegin with, the configuration discussed in the Patent Literature 5 hasno arrangements for implementing signal transmission through theisolation element. Thus it is obvious that the configuration does notdetect any abnormality that may cause malfunctioning in the signaltransmission via the isolation element.

As outlined above, the configurations of the related art have theproblem of not being capable of detecting abnormalities that may causemalfunctioning in the signal transmission via the isolation element. Incase of a malfunction during signal transmission via the isolationelement, the objects to be controlled downstream can operateerroneously, according to the related art. For example, if a malfunctionoccurs during signal transmission via the isolation element, the outputtransistor for controlling the current flowing through the load can beinadvertently turned on, which can cause the load to operateerroneously.

In carrying out the present invention and according to one aspectthereof, there is provided a semiconductor integrated circuit includinga first transmission circuit generating and outputting a firsttransmission signal reflecting a first data signal supplied fromoutside; a first reception circuit reproducing the first data signalbased on a first reception signal; a first isolation element isolatingthe first transmission circuit from the first reception circuit andtransmitting the first transmission signal as the first receptionsignal; an abnormality detection part detecting an abnormality that cancause a malfunction in signal transmission via the first isolation part,and a control part which, upon detection of an abnormality by theabnormality detection party, outputs a stop signal regardless of thefirst data signal supplied from outside to the first transmissioncircuit.

The circuit configuration outlined above detects an abnormality that cancause a malfunction in signal transmission via the isolation element andoutputs a stop signal upon such detection to the object to becontrolled. This prevents the malfunction of the control target.

According to the present invention, it is thus possible to provide asemiconductor integrated circuit which detects an abnormality that cancause a malfunction in signal transmission via the isolation element andwhich issues a stop signal to the object to be controlled to turn offits operation upon such detection, thereby preventing the malfunction ofthe control target.

BRIEF DESCRIPTION OF THE DRAWINGS

Further objects and advantages of the present invention will becomeapparent upon a reading of the following description and appendeddrawings in which:

FIG. 1 is a block diagram showing a typical configuration of asemiconductor integrated circuit as a first embodiment of the presentinvention;

FIG. 2 is a schematic view showing how the semiconductor integratedcircuit as the first embodiment is typically packaged;

FIG. 3 is a timing chart showing typical operations of the semiconductorintegrated circuit as the first embodiment;

FIG. 4 is a timing chart showing other typical operations of thesemiconductor integrated circuit as the first embodiment;

FIG. 5 is a circuit diagram showing a typical configuration of anabnormality detection part in the first embodiment;

FIG. 6 is a circuit diagram showing a typical configuration of a controlpart and some of its peripheral circuitry in the first embodiment;

FIG. 7 is a circuit diagram showing a typical configuration of amagnetic field change detection circuit in the first embodiment;

FIG. 8 is a timing chart showing typical operations of the magneticfield change detection circuit in the first embodiment;

FIG. 9 is a schematic view showing a typical layout of the magneticfield change detection circuit in the first embodiment;

FIG. 10 is a schematic view showing another typical layout of themagnetic field change detection circuit in the first embodiment;

FIG. 11A is a circuit diagram showing a typical configuration of a pulsewidth detection circuit in the first embodiment;

FIG. 11B is a timing chart showing typical operations of the pulse widthdetection circuit in the first embodiment;

FIG. 12 is a circuit diagram showing a variation of the pulse widthdetection circuit in the first embodiment;

FIG. 13A is a circuit diagram showing another typical configuration ofthe pulse width detection circuit in the first embodiment;

FIG. 13B is a timing chart showing typical operations of the pulse widthdetection circuit in FIG. 13A;

FIG. 14A is a circuit diagram showing a typical configuration of acommon mode noise detection circuit in the first embodiment;

FIG. 14B is a timing chart showing typical operations of the common modenoise detection circuit in the first embodiment;

FIG. 15 is a circuit diagram showing a variation of the common modenoise detection circuit in the first embodiment;

FIG. 16 is a circuit diagram showing another typical configuration ofthe common mode noise detection circuit in the first embodiment;

FIG. 17 is a schematic view showing a typical layout of the common modenoise detection circuit in the first embodiment;

FIG. 18 is a schematic view showing another typical layout of the commonmode noise detection circuit in the first embodiment;

FIG. 19A is a circuit diagram showing another typical configuration ofthe common mode noise detection circuit in the first embodiment;

FIG. 19B is a timing chart showing typical operations of the common modenoise detection circuit in FIG. 19A;

FIG. 20 is a circuit diagram partially showing a variation of thesemiconductor integrated circuit as the first embodiment;

FIG. 21 is a circuit diagram also showing partially the variation of thesemiconductor integrated circuit as the first embodiment;

FIG. 22 is a circuit diagram showing a typical configuration of apower-on reset circuit in the first embodiment;

FIG. 23 is a timing chart showing typical operations of the power-onreset circuit in the first embodiment;

FIG. 24 is a circuit diagram showing a typical configuration of alow-voltage detection circuit in the first embodiment;

FIG. 25 is a graphic representation explanatory of the workings of thelow-voltage detection circuit in the first embodiment;

FIG. 26 is a timing chart showing typical operations of the low-voltagedetection circuit in the first embodiment;

FIG. 27 is a circuit diagram showing a typical configuration of a powersource noise detection circuit in the first embodiment;

FIG. 28 is a timing chart showing typical operations of the power sourcenoise detection circuit in the first embodiment;

FIG. 29 is a schematic view showing how the semiconductor integratedcircuit of the present invention is typically packaged;

FIG. 30 is another schematic view showing how the semiconductorintegrated circuit of the present invention is typically packaged;

FIG. 31 is another schematic view showing how the semiconductorintegrated circuit of the present invention is typically packaged;

FIG. 32 is another schematic view showing how the semiconductorintegrated circuit of the present invention is typically packaged;

FIG. 33 is another schematic view showing how the semiconductorintegrated circuit of the present invention is typically packaged;

FIG. 34 is another schematic view showing how the semiconductorintegrated circuit of the present invention is typically packaged;

FIG. 35 is another schematic view showing how the semiconductorintegrated circuit of the present invention is typically packaged;

FIG. 36 is another schematic view showing how the semiconductorintegrated circuit of the present invention is typically packaged;

FIG. 37 is another schematic view showing how the semiconductorintegrated circuit of the present invention is typically packaged;

FIG. 38 is another schematic view showing how the semiconductorintegrated circuit of the present invention is typically packaged;

FIG. 39 is another schematic view showing how the semiconductorintegrated circuit of the present invention is typically packaged;

FIG. 40 is another schematic view showing how the semiconductorintegrated circuit of the present invention is typically packaged;

FIG. 41 is a timing chart showing typical operations of a semiconductorintegrated circuit as a second embodiment of the present invention;

FIG. 42 is a timing chart showing other typical operations of thesemiconductor integrated circuit as the second embodiment;

FIG. 43 is a timing chart showing typical operations of a semiconductorintegrated circuit as a third embodiment of the present invention;

FIG. 44 is a block diagram showing a typical configuration of asemiconductor integrated circuit as a fourth embodiment of the presentinvention;

FIG. 45 is a circuit diagram showing a typical configuration of a commonmode noise detection circuit in the fourth embodiment;

FIG. 46 is a block diagram showing another typical configuration of thesemiconductor integrated circuit as the fourth embodiment;

FIG. 47 is a timing chart showing typical operations of thesemiconductor integrated circuit in FIG. 46;

FIG. 48 is a block diagram showing a typical configuration of asemiconductor integrated circuit as a fifth embodiment of the presentinvention;

FIG. 49 is a block diagram showing a typical configuration of asemiconductor integrated circuit as a sixth embodiment of the presentinvention;

FIG. 50 is a schematic view explanatory of the relations of couplingbetween the semiconductor integrated circuit as the sixth embodiment anda microcomputer;

FIG. 51 is a block diagram showing a typical configuration of asemiconductor integrated circuit as a seventh embodiment of the presentinvention;

FIG. 52 is a schematic view showing how the semiconductor integratedcircuit as the seventh embodiment is typically packaged;

FIG. 53 is another schematic view showing how the semiconductorintegrated circuit as the seventh embodiment is typically packaged;

FIG. 54 is another schematic view showing how the semiconductorintegrated circuit as the seventh embodiment is typically packaged;

FIG. 55 is another schematic view showing how the semiconductorintegrated circuit as the seventh embodiment is typically packaged;

FIG. 56 is another schematic view showing how the semiconductorintegrated circuit as the seventh embodiment is typically packaged;

FIG. 57 is another schematic view showing how the semiconductorintegrated circuit as the seventh embodiment is typically packaged;

FIG. 58 is another schematic view showing how the semiconductorintegrated circuit as the seventh embodiment is typically packaged;

FIG. 59 is a schematic view showing a typical layout of thesemiconductor integrated circuit as the seventh embodiment;

FIG. 60 is a schematic view showing another typical layout of thesemiconductor integrated circuit as the seventh embodiment;

FIG. 61 is a timing chart showing typical operations of thesemiconductor integrated circuit as the seventh embodiment;

FIG. 62 is a schematic view showing inverter equipment to which thepresent invention may be applied, and

FIG. 63 is a timing chart showing typical operations of the inverterequipment to which the present invention may be applied.

DETAILED DESCRIPTION

Some preferred embodiments of the present invention will now bedescribed by reference to the accompanying drawings. These drawings areonly for purpose of simplification and illustration and should not beconstrued as limitative of the present invention. In the ensuingparagraphs and in the drawings, like reference characters designate likeor corresponding component parts of which the explanations will beomitted where redundant.

First Embodiment

FIG. 1 shows a typical configuration of a semiconductor integratedcircuit 1 as the first embodiment of the present invention. Thesemiconductor integrated circuit 1 embodying the invention has theability to detect an abnormality that can cause a malfunction in signaltransmission via an isolation element and to forcibly turn off a powertransistor (a typical target to be controlled) upon such detection.Explained below is an example in which a data signal reproduced by areception circuit controls on/off operations of the power transistor. Itshould be noted that the power transistor is not limitative of thetarget to be controlled using the data signal reproduced by thereception circuit.

The semiconductor integrated circuit 1 shown in FIG. 1 includes atransmission circuit (first transmission circuit) Tx1, a receptioncircuit (second reception circuit) Rx1, an isolation element (firstisolation element) ISO1, a gate driver GD1, an abnormality detectionpart DT1, and a control part CT1. FIG. 1 also shows a power transistor(output transistor) PTr1 as the target to be controlled usingtransmission data VIN (first data signal) reproduced by the receptioncircuit Rx1. The power transistor PTr1 is provided between a sourcevoltage terminal to which a source voltage HVDD is supplied (theterminal is simply called the source voltage terminal HVDD hereunder) onthe one hand, and a load (not shown) on the other hand. The conductionstate of the power transistor PTr1 is controlled using a gate controlsignal (to be discussed later) OUT supplied to the gate (controlterminal) of the transistor. When in the conducting state, the powertransistor PTr1 outputs a load drive signal Vcm to the load.

The transmission circuit Tx1 is included in a semiconductor chip (firstsemiconductor chip) CHP0. The semiconductor chip CHP0 is driven by afirst power source (with source voltage VDD0 and ground voltage GND0)belonging to a first power source system.

The isolation element ISO1, reception circuit Rx1, gate driver GD1,abnormality detection part DT1, and control part CT1 are included inanother semiconductor chip (second semiconductor chip) CHP1. Thesemiconductor chip CHP1 is driven by a second power source (with sourcevoltage VDD1 and ground voltage GND1) belonging to a second power sourcesystem different from the power source system of the semiconductor chipCHP0.

The ensuing explanation will center on the case where the isolationelement ISO1 is an inductor type isolator comprised of a primary sidecoil L11 and a secondary side coil L12 (the element is simply called thetransformer hereunder). However, the transformer is not limitative ofthe isolation element. A capacitor-coupled isolator (simply called thecapacitor hereunder), a GMR element isolator, or a photo-coupler mayalso be used as the isolation element. The same holds for otherisolation elements (ISO2 through ISO4, to be discussed later) apart fromthe isolation element ISO1. The transformer is an AC coupling elementthat uses the primary side coil L11 to convert an electric signal tomagnetism and utilizes the secondary side coil L12 to convert themagnetism to an electric signal thereby transmitting an AC signal fromthe primary side coil L11 to the secondary side coil L12.

A parasitic coupling capacitance Cc is provided between the primary sidecoil L11 and the secondary side coil L12. The parasitic couplingcapacitance is a capacitor with dielectric films comprised of anisolator that fills the spacing between the metallic wiring forming theprimary side coil L11 on the one hand and the metallic wiring making upthe secondary side coil L12 on the other hand.

When the transmission circuit Tx1 outputs a positive amplitude pulsesignal as a transmission signal, a positive amplitude pulse signaldevelops at one end of the secondary side coil L12 and a negativeamplitude pulse signal appears at the other end of the same coil L12.When the transmission circuit Tx1 outputs a negative amplitude pulsesignal as the transmission signal, a negative amplitude pulse signaldevelops at one end of the secondary side coil L12 and a positiveamplitude pulse signal appears at the other end of the same coil L12.Thus the pulse signals with their amplitude directions different fromeach other develop at both ends of the secondary side coil L12. In otherwords, the pulse signals that are inverse to each other relative to theamplitude center potential appear at both ends of the secondary sidecoil L12. Meanwhile, an in-phase common mode voltage is overlaid overboth ends of the secondary side coil L12. In the ensuing paragraphs, theamplitude status at only one of the two ends of the secondary side coilL12 may be explained where appropriate.

FIG. 2 shows how the semiconductor integrated circuit 1 is typicallypackaged. FIG. 2 illustrates primarily how the transmission circuit,reception circuit, and isolation element ISO1 provided therebetween arepackaged. As such, FIG. 2 does not indicate the control part CT1 andabnormality detection part DT1.

The packaged state in FIG. 2 shows the semiconductor chips CHP0 and CHP1included in a semiconductor package PKG0. The semiconductor chips CHP0and CHP1 have a pad Pd each. The pads Pd of the semiconductor chips CHP0and CHP1 are coupled using bonding wires, not shown, to a plurality oflead terminals (external terminals) T furnished over the semiconductorpackage PKG0.

As shown in FIG. 2, the transmission circuit Tx1 is included in thesemiconductor chip CHP0. The reception circuit Rx1, primary side coilL11, secondary side coil L12, and gate driver GD1 are included in thesemiconductor chip CHP1. The semiconductor chip CHP0 also includes padscoupled to the output of the transmission circuit Tx1, and thesemiconductor chip CHP1 includes pads coupled to both ends of theprimary side coil L11. By way of these pads and bonding wires W, thetransmission circuit Tx1 is coupled to the primary side coil L11 formedover the semiconductor chip CHP1.

In the example shown in FIG. 2, the primary side coil L11 and secondaryside coil L12 are formed, respectively, in a first wiring layer and asecond wiring layer stacked one on top the other within onesemiconductor chip.

Also explained below by reference to FIG. 1 is a typical detailedconfiguration of the semiconductor integrated circuit 1. Thetransmission circuit Tx1 operates from the first power source belongingto the first power source system. The reception circuit Rx1, gate driverGD1, abnormality detection part DT1, and control part CT1 operate fromthe second power source belonging to the second power source system.

The transmission circuit Tx1 converts the transmission data VIN to apulse signal that is output as a transmission signal. The isolationelement ISO1 forwards the transmission signal from the transmissioncircuit Tx1 to the reception circuit Rx1 as a reception signal.Specifically, the transmission signal output from the transmissioncircuit Tx1 is first converted to a magnetic signal by the primary sidecoil L11. The secondary side coil L12 generates a reception signalhaving a voltage level reflecting the magnetic field change of theprimary side coil L11 and outputs the generated signal to the receptionsignal Rx1. Thus the transmission signal from the transmission circuitTx1 is sent via the isolation element ISO1 to the reception circuit Rx1as the reception signal.

Based on the reception signal from the isolation element ISO1, thereception circuit Rx1 reproduces the transmission data VIN and outputsthe reproduced data as output data VOUT.

The abnormality detection part DT1 detects an abnormality that can causea malfunction in signal transmission via the isolation element ISO1 andoutputs a detection result ER1. For example, upon detection of anabnormality, the abnormality detection part DT1 outputs a high-leveldetection result ER1. When no such abnormality is detected, theabnormality detection part DT1 outputs a low-level detection result ER1.The abnormality detection part DT1 will be discussed later in moredetail.

Upon detection of an abnormality by the abnormality detection part DT1,the control part CT1 outputs a stop signal to turn off the powertransistor PTr1 regardless of the output data VOUT from the receptioncircuit Rx1. In other words, if the abnormality detection part DT1detects an abnormality, the control part CT1 outputs a stop signal toturn off the power transistor PTr1 regardless of the transmission dataVIN supplied to the transmission circuit Tx1 from outside. For example,when the detection result ER1 is at the high level, the control partoutputs a low-level stop signal regardless of the output data VOUT(i.e., regardless of the transmission data VIN). When the detectionresult ER1 is at the low level, the control part CT1 outputs the outputdata VOUT unchecked.

The gate driver GD1 drives the output signal from the control part CT1so as to output a gate control signal OUT. At the power transistor PTr1,the collector is supplied with the source voltage HVDD having a voltagevalue higher than the source voltage VDD1, and the gate is fed with thegate control signal OUT from the gate driver GD1. The emitter of thepower transistor PTr1 outputs the load drive signal Vcm.

Thus if the detection result ER1 from the abnormality detection part DT1is at the low level, i.e., if any abnormality that can cause amalfunction in signal transmission via the isolation element ISO1 is notdetected, the conduction state of the power transistor PTr1 iscontrolled on the basis of the output data VOUT from the receptioncircuit Rx1. At this point, the power transistor PTr1 may be turned onwhen the output data VOUT is at the high level and turned off when theoutput data VOUT is at the low level, for example.

Meanwhile, if the detection result ER1 from the error detection part DT1is at the high level, i.e., if an abnormality that can cause amalfunction in signal transmission via the isolation element ISO1 isdetected, the power transistor PTr1 is controlled to be forcibly turnedoff regardless of the output data VOUT.

(Timing Chart)

Explained below by reference to FIG. 3 are some typical workings of thesemiconductor integrated circuit as the first embodiment of theinvention. FIG. 3 is a timing chart showing typical operations of thesemiconductor integrated circuit 1. The method of signal transmissionillustrated in FIG. 3 may be adopted when the AC coupling element suchas the transformer, capacitor, or GMR element isolator is used as theisolation element ISO1. The signal transmission method shown in FIG. 3is used not only for signal transmission via the isolation element ISO1but also for signal transmission through other isolation elements to bediscussed later.

In the example of FIG. 3, the transmission circuit Tx1 outputs apositive amplitude pulse signal as the transmission signal insynchronism with a rising edge of the transmission data VIN and anegative amplitude pulse signal as the transmission signal insynchronism with a falling edge of the transmission data VIN. Theisolation element ISO1 forwards the transmission signal from thetransmission circuit Tx1 as the reception signal to the receptioncircuit Rx1. On receiving the positive amplitude pulse signal as thereception signal, the reception circuit Rx1 drives the output data VOUThigh; upon receipt of the negative amplitude pulse signal as thereception signal, the reception circuit Rx1 drives the output data VOUTlow. In this manner, the reception circuit Rx1 reproduces thetransmission data VIN to output the output data VOUT.

According to the signal transmission method shown in FIG. 3, thereception circuit Rx1 may have a hysteresis comparator as anoutput-stage circuit, for example. When the voltage level of thereception signal (or its equivalent) is higher than a threshold voltageVth+ on the high-level side, the hysteresis comparator outputshigh-level output data VOUT. When the voltage level of the receptionsignal (or its equivalent) is lower than a threshold voltage Vth− on thelow-level side, the hysteresis comparator outputs low-level output dataVOUT. Thus on receiving the positive amplitude pulse signal as thereception signal, the hysteresis comparator drives the output data VOUThigh; upon receipt of the negative amplitude pulse signal as thereception signal, the hysteresis comparator drives the output data VOUTlow.

As shown in FIG. 3, the transmission data VIN changes from low level tohigh level at time t1. This causes the transmission circuit Tx1 tooutput a positive amplitude pulse signal as the transmission signal (attime t1). On receiving the positive amplitude pulse signal as thereception signal, the reception circuit Rx1 drives the output data VOUThigh (at time t1). At this point, there is no abnormality that may causea malfunction in signal transmission via the isolation element ISO1.Consequently the abnormality detection part DT1 outputs a low-leveldetection result ER1. Thus the control part CT1 outputs the output dataVOUT from the reception circuit Rx1 unchecked. Since the output dataVOUT is at the high level, the gate control signal OUT also becomeshigh, which turns on the power transistor PTr1.

Suppose that there has since occurred an abnormality that can cause amalfunction in signal transmission via the isolation element ISO1. Inthis case, the abnormality detection part DT1 outputs a high-leveldetection result ER1 as long as the abnormality is present (from time t2to time t3). Thus the control part CT1 outputs a low-level stop signalregardless of the output data VOUT (i.e., regardless of the transmissiondata VIN). This drives the gate control signal OUT low, which forciblyturns off the power transistor PTr1.

When the abnormality disappears, the abnormality detection part DT1changes the detection result ER1 from high level to low level (at timet3). This causes the control part CT1 to again start outputting theoutput data VOUT from the reception circuit Rx1 unchecked. That is, thecontrol part CT1 cancels the stop signal. Because the output data VOUTis at the high level, the gate control signal OUT also becomes high,which turns on the power transistor PTr1 (from time t3 to time t4).

Thereafter, the transmission data VIN changes from high level to lowlevel at time t4. This causes the transmission circuit Tx1 to output anegative amplitude pulse signal as the transmission signal (at time t4).On receiving the negative amplitude pulse signal as the receptionsignal, the reception circuit Rx1 drives the output data VOUT low (attime t4). At this point, there is no abnormality that may cause amalfunction in signal transmission via the isolation element ISO1.Consequently the abnormality detection part DT1 outputs a low-leveldetection result ER1. Thus the control part CT1 outputs the output dataVOUT from the reception circuit Rx1 unchecked. Since the output dataVOUT is at the low level, the gate control signal OUT also becomes low,which turns off the power transistor PTr1.

Suppose that there later occurred an abnormality that can cause amalfunction in signal transmission via the isolation element ISO1. Inthis case, the abnormality detection part DT1 outputs a high-leveldetection result ER1 as long as the abnormality is present (from time t5to time t6). Thus the control part CT1 outputs a low-level stop signalregardless of the output data VOUT (i.e., regardless of the transmissiondata VIN). This drives the gate control signal OUT low, which forciblyturns off the power transistor PTr1. That is, the power transistor PTr1is kept turned off.

When the abnormality disappears, the abnormality detection part DT1changes the detection result ER1 from high level to low level (at timet6). This causes the control part CT1 to again start outputting theoutput data VOUT from the reception circuit Rx1 unchecked. That is, thecontrol part CT1 cancels the stop signal. Because the output data VOUTis at the low level, the gate control signal OUT also becomes low, whichkeeps the power transistor PTr1 off (at time t6).

As explained above, upon detection of an abnormality that can cause amalfunction in signal transmission via the isolation element ISO1 on theside of the semiconductor chip CHP1, the semiconductor integratedcircuit 1 embodying the present invention forcibly turns off the powertransistor PTr1 that is the target to be controlled. The inventivesemiconductor integrated circuit 1 thus prevents the power transistorPTr1 from getting inadvertently turned on and thereby forestalls themalfunction of the load.

The first embodiment above was shown having the control part CT1furnished separately from the reception circuit Rx1. Alternatively, thecontrol part CT1 may be incorporated as part of the reception circuitRx1. The same holds for the relationship between other control parts tobe discussed later on the one hand and the reception circuit on theother hand. For example, the control part CT1 may be incorporated in thehysteresis comparator attached to the reception circuit Rx1. Thehysteresis comparator is configured to output the low-level output dataVOUT in synchronism with a rising edge of the detection result ER1. Inthis case, even when the detection result ER1 changes from high level tolow level following disappearance of the abnormality, the receptioncircuit Rx1 keeps outputting the low-level output data VOUT until alogical value change occurs in the transmission data VIN (see FIG. 4).In other words, after the abnormality detected by the abnormalitydetection part is no longer detected, the reception circuit Rx1 cancelsthe stop signal in synchronism with a first logical value change in thetransmission data VIN.

(Typical Configurations of the Abnormality Detection Part DT1 andControl Part CT1)

FIG. 5 shows a typical configuration of the abnormality detection partDT1. As shown in FIG. 5, the abnormality detection part DT1 has aplurality of detection circuits for detecting an abnormality that cancause a malfunction in signal transmission via the isolation elementISO1. Specifically, the abnormality detection part DT1 includes amagnetic field change detection circuit 101, a pulse width detectioncircuit 102, a common mode noise detection circuit 103, and an ORcircuit 104 that outputs the OR of the results from these circuits asthe detection result ER1. When at least one of these detection circuitshas detected an abnormality, the abnormality detection part DT1 outputsa high-level detection result ER1. When none of the detection circuitsdetects an abnormality, the abnormality detection part DT1 outputs alow-level detection result ER1.

FIG. 6 shows a specific configuration of the control part CT1 and someof its peripheral circuitry. As shown in FIG. 6, the control part CT1has an AND circuit 112 that outputs the AND of the output data VOUT fromthe reception circuit Rx1 and of a reversal value of the detectionresult ER1 from the abnormality detection circuit DT1.

For example, when the detection result ER1 is at the low level, i.e.,when any abnormality that can cause a malfunction in signal transmissionvia the isolation element ISO1 is not detected, the AND circuit 112outputs the output data VOUT unchecked to the gate driver GD1. Thisallows the conduction state of the power transistor PTr1 to becontrolled in accordance with the output data VOUT from the receptioncircuit Rx1. On the other hand, when the detection result ER1 is at thehigh level, i.e., when an abnormality that can cause a malfunction insignal transmission via the isolation element ISO1 is detected, the ANDcircuit 112 outputs a low-level stop signal to the gate driver GD1regardless of the output data VOUT (i.e., regardless of the transmissiondata VIN). This causes the power transistor PTr1 to be forcibly turnedoff.

What follows are explanations of specific configurations of thedetection circuits in the abnormality detection circuit DT1 and theirtypical operations.

(Magnetic Field Change Detection Circuit 101)

The magnetic field change detection circuit 101 is a circuit thatdetects magnetic field changes exceeding a predetermined thresholdrange. In the transformer used as the isolation element ISO1, anelectromotive force is induced in keeping with magnetic field changes.An increasing magnetic field change leading to a growing inducedelectromotive force can trigger a malfunction in signal transmission viathe isolation element ISO1. Thus if the induced electromotive forcecaused by the magnetic field change exceeds the predetermined thresholdrange, the magnetic field change detection circuit 101 determines thatan abnormality that would potentially cause a malfunction in signaltransmission via the isolation element ISO1 has occurred.

FIG. 7 shows a typical configuration of the magnetic field changedetection circuit 101. FIG. 8 is a timing chart showing typicaloperations of the magnetic field change detection circuit 101. As shownin FIG. 7, the magnetic field change detection circuit 101 includes acoil 1011, comparators 1012 through 1014, and an OR circuit 1015. Anelectromotive force reflecting magnetic field changes is induced in thecoil 1011. A potential difference corresponding to the magnetic fieldchange then develops between the two ends of the coil 1011. Thecomparator 1012 outputs the result of the comparison reflecting thepotential difference between the two ends of the coil 1011.

The comparator 1013 compares the threshold voltage Vth+ on thehigh-level side with the comparison result from the comparator 1012 andoutputs the result of the comparison. The comparator 1014 compares thethreshold voltage Vth− on the low-level side with the comparison resultfrom the comparator 1012 and outputs the result of the comparison. TheOR circuit 1015 outputs the OR of the comparison result from thecomparator 1013 and of the comparison result from the comparator 1014 asa detection result E1.

If the electromotive force induced in the coil by the magnetic fieldchange falls within the predetermined threshold range (Vth− throughVth+), the magnetic field change detection circuit 101 determines thatany abnormality that can cause a malfunction in signal transmission viathe isolation element ISO1 has not occurred, and outputs a low-leveldetection result E1. If the electromotive force induced in the coil bythe magnetic field change exceeds the predetermined threshold range, themagnetic field change detection circuit 101 determines that anabnormality that can cause a malfunction in signal transmission via theisolation element ISO1 has occurred and outputs a high-level detectionresult E1.

Incidentally, the magnetic field change detection circuit 101 detectsabnormalities effectively regarding the type of isolation element 1501that is vulnerable to the effects of magnetic fields. Specifically, themagnetic field change detection circuit 101 detects abnormalitieseffectively where the transformer or GMR element isolator is used as theisolation element ISO1.

FIGS. 9 and 10 show typical layouts of the magnetic field changedetection circuit 101. As shown in FIGS. 9 and 10, the coil of themagnetic field change detection circuit 101 should preferably bepositioned close to the isolation element ISO1 so that the coil will beexposed to magnetic fields at a level equivalent to that of the magneticfields sustained by the isolation element ISO1. FIG. 10 shows a typicallayout in which the isolation element ISO1 is formed on the side of thesemiconductor chip CHP0.

(Pulse Width Detection Circuit 102)

The pulse width detection circuit 102 is a circuit that detects whetherthe interval between logical value changes in the reproducedtransmission data VIN (i.e., output data VOUT) has become longer than apredetermined interval. In other words, the pulse width detectioncircuit 102 detects whether the pulse width of the output data VOUT hasbecome greater than a predetermined width. Ordinarily, the signal forcontrolling the power transistor PTr1 is PWM-modulated so that its pulsewidth does not become greater than the predetermined width. That is, thepower transistor PTr1 is not kept turned on longer than thepredetermined interval. If the pulse width of the output data VOUT isgreater than the predetermined width, there is a possibility that amalfunction has occurred in signal transmission via the isolationelement ISO1. For that reason, if the pulse width of the output dataVOUT turns out to be greater than the predetermined width, the pulsewidth detection circuit 102 determines that an abnormality that cancause a malfunction in signal transmission via the isolation elementISO1 has occurred.

FIG. 11A shows a typical configuration of the pulse width detectioncircuit 102. FIG. 11B is a timing chart showing typical operations ofthe pulse width detection circuit 102. As shown in FIG. 11A, the pulsewidth detection circuit 102 includes an isolation part 1021, a pulsedetection part 1022, an OR circuit 1023, and a timer 1024. The pulsedetection part 1022 has comparators 1025 through 1027.

The isolation part 1021 is configured the same as the isolation elementISO1. The isolation part 1021 forwards the transmission signal from thetransmission circuit Tx1 to the pulse detection part 1022 as receptionsignals (Sig+, Sig−).

In the pulse detection part 1022, the comparator 1025 outputs the resultof the comparison reflecting the potential difference between thereception signals (Sig+, Sig−) from the isolation part 1021. Thecomparator 1026 compares the threshold voltage Vth+ on the high-levelside with the comparison result from the comparator 1025 and outputs theresult of the comparison. The comparator 1027 compares the thresholdvoltage Vth− on the low-level side with the comparison result from thecomparator 1025 and outputs the result of the comparison. The OR circuit1023 outputs the OR of the comparison result from the comparator 1026and of the comparison result from the comparator 1027 as a reset signalRST. Thus the reset signal RST is driven high every time a positiveamplitude pulse signal and a negative amplitude pulse signal aretransmitted as reception signals.

For example, the timer 1024 performs a count operation in synchronismwith a clock signal CLK for counting purposes. Alternatively, the timer1024 performs a count operation based on a constant current or aconstant voltage for driving a time constant circuit. When the countvalue reaches a predetermined threshold value, the timer 1024 outputs ahigh-level detection result E2; otherwise the timer 1024 outputs alow-level detection result E2. The timer 1024 resets the count value to“0” in synchronism with a rising edge of the reset signal RST. Thus whenthe interval between rising edges of the reset signal RST is within apredetermined interval, i.e., when the interval between logical valuechanges in the reproduced transmission data VIN (output data VOUT) iswithin a predetermined interval, the timer 1024 resets the count valueto “0” before the count value reaches the threshold value. Consequentlythe detection result E1 is kept at the low level. On the other hand, ifthe interval between rising edges of the reset signal RST exceeds thepredetermined interval, i.e., if the interval between logical valuechanges in the reproduced transmission data VIN (output data VOUT)exceeds the predetermined interval, the detection result E2 becomes highbecause the count value on the timer 1024 has reached the thresholdvalue.

As explained above, when the interval between logical value changes inthe reproduced transmission data VIN (output data VOUT) is within thepredetermined interval, the pulse width detection circuit 102 determinesthat any abnormality that can cause a malfunction in signal transmissionvia the isolation element ISO1 has not occurred, and outputs thelow-level detection result E2. On the other hand, if the intervalbetween logical value changes in the reproduced transmission data VIN(output data VOUT) exceeds the predetermined interval, the pulse widthdetection circuit 102 determines that an abnormality that can cause amalfunction in signal transmission via the isolation element ISO1 hasoccurred and outputs the high-level detection result E2.

(Variation of the Pulse Width Detection Circuit 102)

The pulse width detection circuit 102 can detect abnormalities not onlywhen the transformer is used as the isolation element ISO1 but alsowhere the capacitor, GMR element isolator, or photo-coupler is utilizedas the isolation element ISO1. In these cases, the configuration of theisolation part 1021 is changed in keeping with the configuration of theisolation element ISO1. For example, if the capacitor is used as theisolation part ISO1, the isolation part 1021 is replaced with anisolation part 1028 comprised of a capacitor as shown in FIG. 12.

(Another Typical Configuration of the Pulse Width Detection Circuit)

FIG. 13A shows another typical configuration of the pulse widthdetection circuit 102 as a pulse width detection circuit 102 a. FIG. 13Bis a timing chart showing typical operations of the pulse widthdetection circuit 102 a. As shown in FIG. 13A, the pulse width detectioncircuit 102 a includes a logical value change detection circuit 1028 anda timer 1024. The logical value change detection circuit 1028 has adelay buffer 1029 and an exclusive-OR circuit 1030.

In the logical value change detection circuit 1028, the delay buffer1029 outputs the output data VOUT from the reception circuit Rx1 afterdelaying it by a predetermined time period Td. The exclusive-OR circuit1030 outputs the exclusive-OR of the output data VOUT and of the outputfrom the delay buffer 1029 as a reset signal RST. Thus the exclusive-ORcircuit 1030 drives the reset signal RST high in response to a logicalvalue change in the output data VOUT and drives the reset signal RST lowupon elapse of the predetermined time period Td. That is, the logicalvalue change detection circuit 1028 drives the reset signal RST highevery time the output data VOUT develops a logical value change.

The operation of the timer 1024 was explained above and thus will not bediscussed further.

The pulse width detection circuit 102 a shown in FIG. 13A also providesthe same effects as the pulse width detection circuit 102 in FIG. 11A.In particular, unlike the pulse width detection circuit 102, the pulsewidth detection circuit 102 a has no need for an isolation part and thuscan minimize the increase in circuitry size. Also, the pulse widthdetection circuit 102 a is easier to configure than the pulse widthdetection circuit 102. Furthermore, the pulse width detection circuit102 a can be used as the abnormality detection part regardless of thetype of the isolation element ISO1 in use. That means the pulse widthdetection circuit 102 a can also be used as the abnormality detectionpart in conjunction with a non-pulse time isolation element such as thephoto-coupler. The configuration shown in FIG. 13A is not limitative ofthe pulse width detection circuit 102 a; the pulse width detectioncircuit 102 a may be configured differently while still offeringequivalent functions.

(Common Mode Noise Detection Circuit 103)

The common mode noise detection circuit 103 is a circuit that detectswhether common mode noise has exceeded a predetermined threshold range.Common mode noise refers to the noise generated due to the voltagedifference (i.e., common mode voltage) between two power sources, onepower source driving one semiconductor chip and the other power sourcedriving another semiconductor chip. In this example, the common modenoise is the noise of which the cause is attributable to the voltagedifference (common mode voltage) between a first power source (e.g.,ground voltage UNDO) driving the semiconductor chip CHP0 and a secondpower source (e.g., ground voltage GND1) driving the semiconductor chipCHP1. As fluctuations in the common mode voltage become more pronounced,the inter-power-source noise starts getting generated due to theparasitic coupling capacitance Cc produced in the isolation elementISO1, which may cause a malfunction in signal transmission via theisolation element ISO1. Thus if the common mode noise has exceeded thethreshold range, the common mode noise detection circuit 103 determinesthat an abnormality that can cause a malfunction in signal transmissionvia the isolation element ISO1 has occurred.

FIG. 14A is a typical configuration of the common mode noise detectioncircuit 103. FIG. 14B is a timing chart showing typical operations ofthe common mode noise detection circuit 103. The common mode noisedetection circuit 103 shown in FIG. 14A includes an isolation part 1031,an adder circuit 1032, comparators 1033 and 1034, and an OR circuit1035.

The isolation part 1031 is configured the same as the isolation elementISO1. The isolation part 1031 forwards the transmission signal from thetransmission circuit Tx1 to the adder circuit 1032 as reception signals(Sig+, Sig−).

The adder circuit 1032 adds up the voltage of the reception signal(Sig+) and that of the reception signal (Sig−) to output a sum resultSigSum. The comparator 1033 compares the threshold voltage Vth+ on thehigh-level side with the sum result SigSum from the adder circuit 1032and outputs the result of the comparison. The comparator 1034 comparesthe threshold voltage Vth− on the low-level side with the sum resultSigSum from the adder circuit 1032 and outputs the result of thecomparison. The OR circuit 1035 outputs the OR of the comparison resultfrom the comparator 1033 and of the comparison result from thecomparator 1034 as a detection result E3.

As shown in FIG. 14B, the adder circuit 1032 gets the pulse signaloverlaid on the reception signal (Sig+) and the pulse signal overlaid onthe reception signal (Sig−) to cancel out each other, and adds up thein-phase common mode voltages overlaid on the reception signals (Sig+,Sig−) to output the sum. That is, the sum result SigSum from the addercircuit 1032 is a signal on which only the common mode voltage componentis overlaid. If the sum result SigSum is higher than the thresholdvoltage Vth+, the comparator 1033 outputs a high-level comparisonresult; otherwise the comparator 1033 outputs a low-level comparisonresult. If the sum result SigSum is lower than the threshold voltageVth−, the comparator 1034 outputs a high-level comparison result;otherwise the comparator 1034 outputs a low-level comparison result.Thus if the sum result SigSum exceeds the threshold voltage range ofVth− through Vth+, the OR circuit 1035 outputs a high-level detectionresult E3; otherwise the OR circuit 1035 outputs a low-level detectionresult E3.

As explained above, as long as the common mode noise falls within thepredetermined threshold voltage, the common mode noise detection circuit103 determines that any abnormality that can cause a malfunction insignal transmission via the isolation element ISO1 has not occurred andoutputs the low-level detection result E3. On the other hand, if thecommon mode noise exceeds the predetermined threshold range, the commonmode noise detection circuit 103 determines that an abnormality that cancause a malfunction in signal transmission via the isolation elementISO1 has occurred and outputs the high-level detection result E3.

(Variation of the Common Mode Noise Detection Circuit 103)

The common mode noise detection circuit 103 can detect abnormalities notonly when the transformer is used as the isolation element ISO1 but alsowhere the capacitor, GMR element isolator, or photo-coupler is utilizedas the isolation element ISO1. In these cases, the configuration of theisolation part 1031 is changed in keeping with the configuration of theisolation element ISO1. For example, if the capacitor is used as theisolation part ISO1, the isolation part 1031 is replaced with anisolation part 1036 comprised of a capacitor as shown in FIG. 15.

(Another Typical Configuration of the Common Mode Noise DetectionCircuit)

FIG. 16 is a circuit diagram showing another typical configuration ofthe common mode noise detection circuit 103 in the form of a common modenoise detection circuit 103 a. The common mode noise detection circuit103 a shown in FIG. 16 includes a capacitor 1037 used as the isolationelement, resistance elements 1038 and 1039, and a comparator 1040.

One electrode of the capacitor 1037 is supplied via the resistanceelement 1038 with the ground voltage GND0 that is the first powersource. The other electrode of the capacitor 1037 is fed via theresistance element 1039 with the ground voltage GND1 that is the secondpower source. The comparator 1040 compares a predetermined thresholdvoltage with the voltage on the other electrode (on the second powersource side) of the capacitor 1037 and outputs the result of thecomparison (comparison result E3). Specifically, if the voltage on theother electrode of the capacitor 1037 is higher than the thresholdvoltage, the comparator 1040 outputs the high-level detection result E3;otherwise the comparator 1040 outputs the low-level comparison resultE3.

Just as large fluctuations in the voltage difference (common modevoltage) between the ground voltage GND0 and the ground voltage GND1 cangenerate the inter-power-source noise due to the parasitic couplingcapacitance C1 produced in the isolation element ISO, the capacitor 1037can also incur an inter-power-source noise. This causes the voltage onthe other electrode of the capacitor 1037 to fluctuate. The common modenoise detection circuit 103 a shown in FIG. 16 determines that anabnormality that can cause a malfunction in signal transmission via theisolation element ISO1 has occurred if the capacitor 1037 has generatedthe inter-power-source noise (common mode noise) causing the otherelectrode (second power source side) of the capacitor 1037 to carry avoltage higher than the threshold voltage. That is, if theinter-power-source noise (common mode noise) attributable to thecapacitor 1037 has exceeded the predetermined threshold range, thecommon mode noise detection circuit 103 a shown in FIG. 16 determinesthat an abnormality that can cause a malfunction in signal transmissionvia the isolation element ISO1 has occurred.

Configured as explained above, the common mode noise detection circuit103 a also provides the same effects as the common mode noise detectioncircuit 103 shown in FIG. 14A.

FIGS. 17 and 18 show typical layouts of the common mode noise detectioncircuit 103 a. As shown in FIGS. 17 and 18, the capacitor 1037 of thecommon mode noise detection circuit 103 a should preferably bepositioned close to the isolation element ISO1 so that the noise may begenerated under conditions as similar as possible to those for theisolation element ISO1. FIG. 18 shows a layout example in which both theisolation element ISO1 and the capacitor 1037 are formed on the side ofthe semiconductor chip CHP0.

(Yet Another Typical Configuration of the Common Mode Noise DetectionCircuit)

FIG. 19A is a circuit diagram showing yet another typical configurationof the common mode noise detection circuit 103 in the form of a commonmode noise detection circuit 103 b. FIG. 19B is a timing chart showingtypical operations of the common mode noise detection circuit 103 b. Asshown in FIG. 19A, the common mode noise detection circuit 103 bincludes an isolation part 1031, a low-pass filter 1041, comparators1033 and 1034, and an OR circuit 1035.

As explained above, the isolation part 1031 forwards the transmissionsignal from the transmission circuit Tx1 as a reception circuitSig+(voltage at one end of the secondary side coil).

The low-pass filter 1041 extracts the common mode noise componentoverlaid on the reception signal Sig+ and outputs the extractedcomponent as a signal SigLPF.

If the signal SigLPF from the low-pass filter 1041 is higher than thethreshold voltage Vth+ on the high-level side, the comparator 1033outputs a high-level comparison result; otherwise the comparator 1033outputs a low-level comparison result. If the signal SigLPF from thelow-pass filter 1041 is lower than the threshold voltage Vth− on thelow-level side, the comparator 1034 outputs a high-level comparisonresult; otherwise the comparator 1034 outputs a low-level comparisonresult. Thus when the signal SigLPF (i.e., common mode noise component)from the low-pass filter 1041 exceeds the threshold voltage range ofVth− through Vth+, the OR circuit 1035 outputs the high-level detectionresult E3; otherwise the OR circuit 1035 outputs the low-level detectionresult E3.

The common mode noise detection circuit 103 b shown in FIG. 19A alsoprovides the same effects as the common mode noise detection circuit 103in FIG. 14A.

(Typical Configuration of the Abnormality Detection Part DTX1)

In the examples above, the control part CT1 was explained as outputtingthe stop signal only if the abnormality detection part DT1 has detectedan abnormality. Alternatively, the control part CT1 may be configureddifferently so as to output the stop signal not only when theabnormality is detected by the abnormality detection part DT1 but alsowhere other abnormalities are detected.

FIG. 20 shows a variation of the semiconductor integrated circuit 1,i.e., a configuration of the semiconductor integrated circuit 1supplemented with an abnormality detection part DTX1 for detecting otherabnormalities. FIG. 20 shows only the abnormality detection circuit DT1,abnormality detection circuit DTX1, and an OR circuit 111. The ensuingexplanation will primarily deal with the configuration and operations ofthe abnormality detection part DTX1.

The abnormality detection part DTX1 shown in FIG. 20 includes a power-onreset circuit 105, a low-voltage detection circuit 106, a power sourcenoise detection circuit 107, an overcurrent detection circuit 108, anoverheat detection circuit 109, and an OR circuit 110 that outputs theOR of the detection results from these circuits as a detection resultEX0. When at least one of these detection circuits detects anabnormality, the abnormality detection part DTX1 outputs a high-leveldetection result EX0; when none of the detection circuits detects anabnormality, the abnounality detection part DTX1 outputs a low-leveldetection result EX0. The abnormality detection part DT1 outputs thedetection result BO. The OR circuit 111 outputs the OR of the detectionresult E0 from the abnormality detection part DT1 and of the detectionresult EX0 from the abnormality detection part DTX1 as a detectionresult ER1. FIG. 21 shows typical relations of coupling among theabnormality detection parts DT1 and DTX1, control part CT1, and theirperipheral circuits.

What follows are explanations of specific configurations and operationsof the individual detection circuits provided in the abnormalitydetection part DTX1.

(Power-on Reset Circuit 105)

The power-on reset circuit 105 is a circuit that detects a predeterminedtime period over which the source voltage VDD1 on the side of thesemiconductor chip CHP1 stabilizes after power-on. Immediately afterpower is turned on, the source voltage VDD1 is unstable so that thecircuits powered thereby may not operate normally for a certain period.Thus during a predetermined time period following power-on, the power-onreset circuit 105 determines that an abnormality is taking place.

FIG. 22 shows a typical configuration of the power-on reset circuit 105.FIG. 23 is a timing chart showing typical operations of the power-onreset circuit 105. As shown in FIG. 22, the power-on reset circuit 105includes a resistance element 1051, a capacitor 1052, and an inverter1053.

The resistance element 1051 is provided interposingly between the sourcevoltage terminal to which the source voltage VDD1 is supplied (theterminal is called the source voltage terminal VDD1 hereunder) and anode N1. The capacitor 1052 is provided interposingly between the nodeN1 and the ground voltage terminal to which the ground voltage GND1 issupplied (the terminal is called the ground voltage terminal GND1hereunder). When the voltage Vc of the node N1 is lower than a thresholdvoltage Vth, the inverter 1053 outputs a high-level detection result E5;when the voltage Vc of the node N1 exceeds the threshold voltage Vth,the inverter 1053 outputs a low-level detection result E5.

As shown in FIG. 23, when power is applied and the voltage level of thesource voltage VDD1 is raised (at time t1), the voltage Vc of the nodeN1 starts to rise gradually. For some time following power-on, thevoltage Vc of the node N1 is lower than the threshold voltage Vth.During that time, the inverter 1053 outputs the high-level detectionresult E1 (from time t1 to time t2). When the voltage Vc of the node N1exceeds the threshold voltage Vth, the inverter 1053 outputs thelow-level detection result E5 (at time t2).

As explained above, the power-on reset circuit 105 outputs thehigh-level detection result E5 after power is applied and until apredetermined time period elapses. Upon elapse of the predetermined timeperiod, with the source voltage stabilized, the power-on reset circuit105 outputs the low-level detection result E5.

(Low-Voltage Detection Circuit 106)

The low-voltage detection circuit 106 is a circuit that detects whetherthe voltage level of the source voltage VDD1 on the side of thesemiconductor chip CHP1 is lower than a predetermined threshold value.While the source voltage VDD1 is being lower than the threshold value,the circuits powered thereby may not operate normally. Thus if thevoltage level of the source voltage VDD1 becomes lower than thethreshold value, the low-voltage detection circuit 106 determines thatan abnormality has occurred.

FIG. 24 shows a typical configuration of the low-voltage detectioncircuit 106. FIG. 25 is a graphic representation explanatory of theworkings of the low-voltage detection circuit 106. FIG. 26 is a timingchart showing typical operations of the low-voltage detection circuit106. The low-voltage detection circuit 106 shown in FIG. 24 includes areference voltage generation circuit 1061, comparators 1062 and 1063,and an RS latch 1064. Shown in FIG. 24 is the configuration example inwhich the voltage level of the source voltage VDD1 at stable time is 5V.

The reference voltage generation circuit 1061 generates a firstreference voltage of 4V and a second reference voltage of 4.5V, forexample. The comparator 1062 compares the source voltage VDD1 with thefirst reference voltage and outputs the result of the comparison. Thecomparator 1063 compares the source voltage VDD1 with the secondreference voltage and outputs the result of the comparison. The RS latch1064 outputs from an output terminal Q a detection result E6 based onthe comparison result coming from the comparator 1062 and input to a setterminal S and on the comparison result sent from the comparator 1063and input to a reset terminal R.

As shown in FIG. 26, when the voltage level of the source voltage VDD1is lower than 4.0V (at time t0), the comparator 1062 outputs ahigh-level comparison result and the comparator 1063 outputs a low-levelcomparison result. This causes the RS latch 1064 to output a high-leveldetection result E6. When the voltage level of the source voltage VDD1rises and exceeds 4.0V (at time t1), the comparator changes itscomparison result to the low level but the comparator 1063 holds itslow-level comparison result unchanged. This causes the RS latch 1064 tokeep outputting the high-level detection result. When the voltage levelof the source voltage VDD1 further rises and becomes higher than 4.5V(at time t2), the comparator 1063 changes its comparison result to thehigh level. This causes the RS latch 1064 to change its detection resultE6 to the low-level and output the low-level detection result E6.

Conversely, when the voltage level of the source voltage VDD1 drops andbecomes lower than 4.5V (but higher than 4.0V, at time t3), thecomparator 1063 changes its comparison result to the low level but thecomparator 1062 holds its low-level comparison result unchanged. Thiscauses the RS latch 1064 to keep outputting the low-level detectionresult E6. When the voltage level of the source voltage VDD1 furtherdrops and becomes lower than 4V (at time t4), the comparator 1062changes its comparison result to the high level. This causes the RSlatch 1064 to changes its detection result E6 to the high level andoutput the high-level detection result E6. That is, the low-voltagedetection circuit 106 provides the detection of the source voltage VDD1with a hysteresis characteristic (see FIG. 25).

As explained above, when the voltage level of the source voltage VDD1 ishigher than the predetermined threshold value, the low-voltage detectioncircuit 106 determines that the source voltage VDD1 is stable andoutputs the low-level detection result E6. On the other hand, when thevoltage level of the source voltage VDD1 is lower than the thresholdvalue, the low-level detection circuit 106 determines that the sourcevoltage VDD1 is unstable and outputs the high-level detection result E6.

(Power Source Noise Detection Circuit 107)

The power source noise detection circuit 107 is a circuit that detectswhether the noise of the source voltage VDD1 on the side of thesemiconductor chip CHP1 has exceeded a predetermined threshold range. Ifthe noise of the source voltage VDD1 exceeds the threshold range, thecircuits powered thereby may not operate normally. Thus if the noise ofthe source voltage VDD1 has exceeded the threshold range, the powersource noise detection circuit 107 determines that an abnormality hasoccurred.

FIG. 27 shows a typical configuration of the power source noisedetection circuit 107. FIG. 28 is a timing chart showing typicaloperations of the power source noise detection circuit 107. The powersource noise detection circuit 107 shown in FIG. 27 includes a capacitor1071, an operation amplifier 1072, a resistance element 1073,comparators 1074 and 1075, and an OR circuit 1076.

The capacitor 1071 is provided interposingly between the source voltageterminal VDD1 and the operation amplifier 1072. The resistance element1073 is provided interposingly between the output and the inputterminals of the operation amplifier 1072. That is, the capacitor 1071,operation amplifier 1072, and resistance element 1073 make up aso-called high-pass filter. The comparator 1074 compares the thresholdvoltage Vth+ on the high-level side with the output voltage from theoperation amplifier 1072 and outputs the result of the comparison. Thecomparator 1075 compares the threshold voltage Vth− on the low-levelside with the output voltage from the operation amplifier 1072 andoutputs the result of the comparison. The OR circuit 1076 outputs the ORof the comparison result from the comparator 1074 and of the comparisonresult from the comparator 1075 as a detection result E7.

As shown in FIG. 28, when the noise of the source voltage VDD1 fallswithin the threshold voltage range of Vth− through Vth+, the powersource noise detection circuit 107 determines that the source voltageVDD1 is stable and outputs a low-level detection result E7. On the otherhand, when the noise of the source voltage VDD1 exceeds the thresholdvoltage range of Vth− through Vth+, the power source noise detectioncircuit 107 determines that the source voltage VDD1 is unstable andoutputs a high-level detection result E7.

(Overcurrent Detection Circuit 108)

The overcurrent detection circuit 108 is a circuit that detects whetheran overcurrent flows through the power transistor PTr1. If the currentvalue of the current flowing through the power transistor PTr1 is largerthan a predetermined threshold value, the power transistor PTr1 may bedestroyed or otherwise damaged. Thus if the current value of the currentflowing through the power transistor PTr1 becomes larger than thepredetermined threshold value, the overcurrent detection circuit 108determines that an abnormality has occurred and outputs a high-leveldetection result E8.

(Overheat Detection Circuit 109)

The overheat detection circuit 109 is a circuit that detects whether thetemperature inside or around the semiconductor chip CHP1 has becomehigher than a predetermined threshold temperature. If the temperaturebecomes higher than the threshold value, the circuits may operatenormally. Thus if the temperature inside or around the semiconductorchip CHP1 is higher than the predetermined threshold temperature, theoverheat detection circuit 109 determines that an abnormality hasoccurred and outputs a high-level detection result E9. For example, theoverheat detection circuit 109 may detect the temperature based on thevalue of a forward voltage Vf of diodes located near the object of whichthe temperature is to be measured.

(Other Typical Packaged States of the Semiconductor Integrated Circuit1)

The packaged state shown in FIG. 2 is not limitative of how thetransmission circuit Tx1, reception circuit Rx1, and isolation elementISO1 interposed therebetween are to be packaged. Explained below byreference to FIGS. 29 through 40 are other packaged states of thesemiconductor integrated circuit 1 embodying the present invention.FIGS. 29 through 35 show packaged states in which a transformer is usedas the isolation element ISO1. FIGS. 36 and 37 show packaged state inwhich a capacitor is used as the isolation element ISO1. FIG. 38 shows apackaged state in which a GMR element isolator is used as the isolationelement ISO1. FIGS. 39 and 40 show packaged states in which aphoto-coupler is used as the isolation element ISO1. FIGS. 29 through 40are provided primarily for the purpose of explaining how thetransmission circuit Tx1, reception circuit Rx1, and isolation elementISO1 interposed therebetween are packaged. As such, FIGS. 29 through 40do not show the control part CT1 and abnormality detection part DT1.

In the packaged state shown in FIG. 29, the transmission circuit Tx1 isformed over the semiconductor chip CHP0. The semiconductor chip CHP1includes the reception circuit Rx1, primary side coil L11 and secondaryside coil L12 making up the isolation element ISO1, and gate driver GD1.Also, the semiconductor chip CHP0 has a plurality of pads formed andcoupled to the output of the transmission circuit Tx1. The semiconductorchip CHP1 has pads formed and coupled to both ends of the primary sidecoil L11. By way of these pads and bonding wires W, the transmissioncircuit Tx1 is coupled to the primary side coil L11 formed over thesemiconductor chip CHP1. The center tap of the primary side coil L11 iscoupled to the power supply terminal on the side of the semiconductorchip CHP0 (e.g., ground voltage terminal GND0) by way of a pad and abonding wire w separately provided. The center tap of the secondary sidecoil L12, on the other hand, is coupled to the power supply terminal onthe side of the semiconductor chip CHP1 (e.g., ground voltage terminalGND1).

In the example shown in FIG. 29, the primary side coil L11 and secondaryside coil L12 are formed in a first wiring layer and a second wiringlayer, respectively, which are stacked one on top the other over onesemiconductor chip. The primary side coil L11 is formed by two coilswith the center tap interposed therebetween, and the secondary side coilL12 is also formed by two coils with the center tap interposedtherebetween.

In the packaged state shown in FIG. 30, the transmission circuit Tx1 andthe primary side coil L11 and secondary side coil L12 making up theisolation element ISO1 are formed over the semiconductor chip CHP0. Thereception circuit Rx1 and gate driver GD1 are formed over thesemiconductor chip CHP1. Also, the semiconductor chip CHP0 has padsformed and coupled to both ends of the secondary side coil L12. Thesemiconductor chip CHP1 has pads formed and coupled to the input of thereception circuit Rx1. By way of these pads and bonding wires W, thereception circuit Rx1 is coupled to the secondary side coil L12 formedover the semiconductor chip CHP0.

In the example shown in FIG. 30, the primary side coil L11 and secondaryside coil L12 are formed in a first wiring layer and a second wiringlayer, respectively, which are stacked one on top the other over onesemiconductor chip.

In the packaged state shown in FIG. 31, the transmission circuit Tx1 isformed over the semiconductor chip CHP0. The reception circuit Rx1 andgate driver GD1 are formed over the semiconductor chip CHP1. The primaryside coil L11 and secondary coil L12 making up the isolation elementISO1 are formed over a semiconductor chip CHP3 different from thesemiconductor chips CHP0 and CHP1. Also, the semiconductor chip CHP0 haspads formed and coupled to the output of the transmission circuit Tx1.The semiconductor chip CHP1 has pads formed and coupled to the input ofthe reception circuit Rx1. The semiconductor chip CHP3 has pads formedand coupled to the two ends of the primary side coil L11 as well as padsformed and coupled to both ends of the secondary side coil L12. By wayof these pads and bonding wires W, the transmission circuit Tx1 iscoupled to the primary side coil L11 formed over the semiconductor chipCHP3. Also via these pads and bonding wires W, the reception circuit Rx1is coupled to the secondary side coil L12 formed over the semiconductorchip CHP3.

In the example shown in FIG. 31, the primary side coil L11 and secondaryside coil L12 are formed in a first wiring layer and a second wiringlayer, respectively, which are stacked one on top the other over onesemiconductor chip.

In the packaged state shown in FIG. 32, the transmission circuit Tx1 andprimary side coil L11 are formed over the semiconductor chip CHP0. Thereception circuit Rx1, gate driver GD1, and secondary side coil L12 areformed over the semiconductor chip CHP1. The semiconductor chips CHP0and CHP1 are stacked one on top the other. When stacked, thesemiconductor chips CHP0 and CHP1 are positioned in such a manner thatthe center of the primary side coil L11 and that of the secondary sidecoil L12 are on the same straight line.

In the packaged state shown in FIG. 33, the transmission circuit Tx1,reception circuit Rx1, primary side coil L11 and secondary side coil L12making up the isolation element ISO1, and gate driver GD1 are formedover a common semiconductor chip CHP4. In the example of FIG. 33, theprimary side coil L11 and secondary side coil L12 are formed in a firstwiring layer and a second wiring layer, respectively, which are stackedone on top the other over the semiconductor chip CHP4. The area in whichthe transmission circuit Tx1 is located and the area in which thereception circuit Rx1 are positioned are isolated from each other by anisolation layer formed in the substrate of the semiconductor chip CHP4.

FIGS. 34 and 35 are cross-sectional views of the substrate carrying thesemiconductor chip CHP4 shown in FIG. 33. In the example shown in FIG.34, the area in which the transmission circuit Tx1 is formed and thearea in which the reception circuit Rx1 are formed are cut offelectrically from each other by an isolation layer. The primary sidecoil L11 and secondary side coil L12 are provided in the area where thereception circuit Rx1 is formed. In the example shown in FIG. 35, thearea in which the transmission circuit Tx1 is formed and the area inwhich the reception circuit Rx1 are formed are also cut off electricallyfrom each other by an isolation layer. In this example, the primary sidecoil L11 and secondary side coil L12 are provided in the area where thetransmission circuit Tx1 is formed.

FIG. 36 shows the packaged state of FIG. 2 in which the transformer isreplaced with a capacitor as the isolation element ISO1. Morespecifically, the coil L11 is replaced with one electrode C11 of thecapacitor and the coil L12 with the other electrode C12 thereof. FIG. 37shows the packaged state of FIG. 29 in which the transformer is replacedwith a capacitor as the isolation element ISO1. More specifically, thecoil L11 is replaced with electrodes C11 a and C11 b on one side of thecapacitor and the C12 with electrodes C12 a and C12 b on the other sidethereof.

FIG. 37 shows the packaged state of FIG. 2 in which the transformer isreplaced with a GMR element isolator as the isolation element ISO1. Morespecifically, the coil L11 is left intact while the coil L12 is replacedwith a GMR element R12.

In the packaged state shown in FIG. 39 where a photo-coupler is used asthe isolation element ISO1, a light emitting element D11 is formed overthe semiconductor chip CHP0 while a light receiving part Q12, thereception circuit Rx1, and gate driver GD1 are formed over thesemiconductor chip CHP1. The light emitting element D11 and lightreceiving part Q12 make up the photo-coupler.

FIG. 40 is a cross-sectional view of the semiconductor integratedcircuit shown in FIG. 39. As shown in FIG. 40, the semiconductor chipCHP0 carrying the light emitting element D11 and the semiconductor chipCHP1 carrying the light receiving part Q12 are stacked one on top theother. When thus stacked, the semiconductor chips CHP0 and CHP1 arepositioned so that the light emitting element D11 and light receivingpart Q12 are faced with each other. The gap between the light emittingelement D11 and the light receiving element Q12 is filled with atransparent resin material permitting transmission of light signals fromthe light emitting element D11 to the light receiving part Q12. Theentire assembly is enclosed by a plastic mold that keeps the lightsignals of the light emitting element D11 from leaking out.

As explained above, there are no specific constraints on the type of theisolation element ISO1 or on the layout thereof. Whereas the foregoingparagraphs showed the isolation element ISO1 formed over a semiconductorchip, the isolation element ISO1 may be provided alternatively as anexternal part.

Although the foregoing paragraphs explained the packaged states of thecombination of the transmission circuit Tx1, reception circuit Rx1, andisolation element ISO1 interposed therebetween, this combination is notlimitative of the component parts that may be packaged. Alternatively,other combinations of transmission circuits, reception circuits, andisolation elements interposed therebetween may be packaged in likemanner.

Second Embodiment

Another example of operations of the semiconductor integrated circuit 1is explained below in reference to FIG. 41 as the second embodiment ofthe present invention. FIG. 41 is a timing chart showing typicaloperations of the semiconductor integrated circuit 1 operating on asignal transmission method different from that shown in FIG. 3. Thesignal transmission method shown in FIG. 41 may be adopted when the ACcoupling element such as the transformer, capacitor, or GMR isolator isused as the isolation element ISO1. The signal transmission method shownin FIG. 41 is used not only for the transmission of signals via theisolation element ISO1 but also for signal transmission via otherisolation elements, to be discussed later.

In the example of FIG. 41, the transmission circuit Tx1 outputs twoconsecutive pulse signals (called a two-pulse signal altogether) as atransmission signal in synchronism with a rising edge of transmissiondata VIN. The transmission circuit Tx1 also outputs a single pulsesignal (called a one-pulse signal) as another transmission signal insynchronism with a falling edge of the transmission data VIN. Theisolation element ISO1 forwards the transmission signal coming from thetransmission circuit Tx1 to the reception circuit Rx1 as a receptionsignal. On receiving the two-pulse signal as the reception signal, thereception circuit Rx1 drives output data VOUT high; upon receipt of theone-pulse signal as the reception signal, the reception circuit Rx1drives the output data VOUT low. In this manner, the reception circuitRx1 reproduces the transmission data VIN and outputs the reproduced dataas the output data VOUT.

Where the signal transmission method shown in FIG. 41 is adopted, thereception circuit Rx1 has a high-level detection circuit, a low-leveldetection circuit, and an RS latch, for example. Upon receipt of thetwo-pulse signal as the reception signal, the high-level detectioncircuit drives a set signal high. Upon receipt of the one-pulse signalas the reception signal, the low-level detection circuit drives a resetsignal high. Based on the set signal from the high-level detectioncircuit and on the reset signal from the low-level detection circuit,the RS latch outputs the output data VOUT. That is, the RS latch drivesthe output data VOUT high upon receipt of the two-pulse signal anddrives the output data VOUT low on receiving the one-pulse signal.

As shown in FIG. 41, the transmission data VIN changes from high levelto low level at time t1. This causes the transmission circuit Tx1 tooutput the two-pulse signal as the transmission signal (at time t1).Upon receipt of the two-pulse signal as the reception signal, thereception circuit Rx1 drives the output data VOUT high (time t2). Atthis point, any abnormality that may cause a malfunction signaltransmission via the isolation element ISO1 has not occurred, so thatthe abnormality detection part DT1 outputs a low-level detection resultER1. Thus the control part CT1 outputs the output data VOUT from thereception circuit Rx1 unchecked. Because the output data VOUT is at thehigh level, the gate control signal OUT is also high, which turns on thepower transistor PTr1.

Suppose that there has since occurred an abnormality that can cause amalfunction in signal transmission via the isolation element ISO1. Inthis case, the abnormality detection part DT1 outputs a high-leveldetection result ER1 as long as the abnormality is present (from time t3to time t4). Thus the control part CT1 outputs a low-level stop signalregardless of the output data VOUT (i.e., regardless of the transmissiondata VIN). This drives the gate control signal OUT low, which forciblyturns off the power transistor PTr1.

When the abnormality disappears, the abnormality detection part DT1changes the detection result ER1 from high level to low level (at timet4). This causes the control part CT1 to again start outputting theoutput data VOUT from the reception circuit Rx1 unchecked. That is, thecontrol part CT1 cancels the stop signal. Because the output data VOUTis at the high level, the gate control signal OUT also becomes high,which turns on the power transistor PTr1 (at time t4).

Thereafter, the transmission data VIN changes from high level to lowlevel at time t5. This causes the transmission circuit Tx1 to output theone-pulse signal as the transmission signal (at time t5). On receivingthe one-pulse signal as the reception signal, the reception circuit Rx1drives the output data VOUT low (at time t6). At this point, there is noabnormality that may cause a malfunction in signal transmission via theisolation element ISO1. Consequently the abnormality detection part DT1outputs a low-level detection result ER1. Thus the control part CT1outputs the output data VOUT from the reception circuit Rx1 unchecked.Since the output data VOUT is at the low level, the gate control signalOUT also becomes low, which turns off the power transistor PTr1.

Suppose that there later occurred an abnormality that can cause amalfunction in signal transmission via the isolation element ISO1. Inthis case, the abnormality detection part DT1 outputs a high-leveldetection result ER1 as long as the abnormality is present (from time t7to time t8). Thus the control part CT1 outputs a low-level stop signalregardless of the output data VOUT (i.e., regardless of the transmissiondata VIN). This drives the gate control signal OUT low, which forciblyturns off the power transistor PTr1. That is, the power transistor PTr1is kept turned off.

When the abnormality disappears, the abnormality detection part DT1changes the detection result ER1 from high level to low level (at timet8). This causes the control part CT1 to again start outputting theoutput data VOUT from the reception circuit Rx1 unchecked. That is, thecontrol part CT1 cancels the stop signal. Because the output data VOUTis at the low level, the gate control signal OUT also becomes low, whichkeeps the power transistor PTr1 off (at time t8).

As explained above, the semiconductor integrated circuit 1 adopting thesignal transmission method of the second embodiment offers substantiallythe same effects as those of the first embodiment.

The second embodiment above was shown having the control part CT1furnished separately from the reception circuit Rx1. Alternatively, thecontrol part CT1 may be incorporated as part of the reception circuitRx1. The same holds for the relationship between other control parts tobe discussed later on the one hand and the reception circuit on theother hand. For example, the control part CT1 may be incorporated as anOR circuit in the reception circuit Rx1. The OR circuit outputs the ORof the reset signal from the low-level detection circuit and of thedetection result ER from the abnormality detection part DT1 to the resetterminal R of the RS latch. In this case, even when the detection resultER1 changes from high level to low level following disappearance of theabnormality, the reception circuit Rx1 keeps outputting the low-leveloutput data VOUT until the next logical value change occurs in thetransmission data VIN (see FIG. 42). In other words, after theabnormality detected by the abnormality detection part is no longerdetected, the reception circuit Rx1 cancels the stop signal insynchronism with a first logical value change in the transmission dataVIN.

Third Embodiment

Another example of operations of the semiconductor integrated circuit 1is explained below in reference to FIG. 43 as the second embodiment ofthe present invention. FIG. 43 is a timing chart showing typicaloperations of the semiconductor integrated circuit 1 operating on asignal transmission method different from that shown in FIG. 3 or inFIG. 41. The signal transmission method shown in FIG. 43 may be adoptedwhen the AC coupling element such as the transformer, capacitor, or GMRisolator is used as the isolation element ISO1. The signal transmissionmethod shown in FIG. 43 is used not only for the transmission of signalsvia the isolation element ISO1 but also for signal transmission viaother isolation elements, to be discussed later.

In the example of FIG. 43, the transmission circuit Tx1 outputs pulsesnot multiplexed on the transmission signal when the transmission dataVIN is at the low level, and outputs consecutive pulses multiplexed onthe transmission signal when the transmission data is at the high level.The isolation element ISO1 forwards the transmission signal coming fromthe transmission circuit Tx1 to the reception circuit Rx1 as thereception signal. On receiving the pulse-multiplexed reception signal,the reception circuit Rx1 drives the output data VOUT high; upon receiptof the pulse-free reception signal, the reception circuit Rx1 drives theoutput data VOUT low. In this manner, the reception circuit Rx1reproduces the transmission data VIN and outputs the reproduced data asthe output data VOUT.

As shown in FIG. 43, the transmission data VIN is at the low level attime t0. Thus the transmission circuit Tx1 outputs pulses notmultiplexed on the transmission signal (at time t0). The receptioncircuit x1 outputs the low-level output data VOUT because it isreceiving the pulse-free reception signal (at time t0).

Thereafter, the transmission data VIN changes from low level to highlevel at time t1. This causes the transmission circuit Tx1 to startoutputting continuous pulses multiplexed on the transmission signal (attime t1). On receiving the pulse-multiplexed reception signal, thereception circuit Rx1 drives the output data high (at time t1). At thispoint, any abnormality that can cause a malfunction in signaltransmission via the isolation element ISO1 has not occurred, so thatthe abnormality detection part DT1 outputs a low-level detection resultER1. Thus the control part CT1 outputs the output data VOUT from thereception circuit Rx1 unchecked. Because the output data VOUT is at thehigh level, the gate control signal OUT is also high, which turns on thepower transistor PTr1.

Suppose that there later occurred an abnormality that can cause amalfunction in signal transmission via the isolation element ISO1. Inthis case, the abnormality detection part DT1 outputs a high-leveldetection result ER1 as long as the abnormality is present (from time t2to time t3). Thus the control part CT1 outputs a low-level stop signalregardless of the output data VOUT (i.e., regardless of the transmissiondata VIN). This drives the gate control signal OUT low, which forciblyturns off the power transistor PTr1.

When the abnormality disappears, the abnormality detection part DT1changes the detection result ER1 from high level to low level (at timet3). This causes the control part CT1 to again start outputting theoutput data VOUT from the reception circuit Rx1 unchecked. Because theoutput data VOUT is at the high level, the gate control signal OUT alsobecomes high, which turns on the power transistor PTr1 (from time t3 tot4).

Thereafter, the transmission data VIN changes from high level to lowlevel at time t4. This causes the transmission circuit Tx1 to startoutputting pulses not multiplexed on the transmission signal (at timet4). Upon receipt of the pulse-free reception signal, the receptioncircuit Rx1 drives the output data VOUT low (at time t4). At this point,any abnormality that can cause a malfunction in signal transmission viathe isolation element ISO1 has not occurred, so that the abnormalitydetection part DT1 outputs a low-level detection result ER1. Thus thecontrol part CT1 outputs the output data VOUT from the reception circuitRx1 unchecked. Because the output data VOUT is at the low level, thegate control signal OUT is also low, which turns off the powertransistor PTr1.

Suppose that there later occurred an abnormality that can cause amalfunction in signal transmission via the isolation element ISO1. Inthis case, the abnormality detection part DT1 outputs a high-leveldetection result ER1 as long as the abnormality is present (from time t5to time t6). Thus the control part CT1 outputs a low-level stop signalregardless of the output data VOUT (i.e., regardless of the transmissiondata VIN). This drives the gate control signal OUT low, which forciblyturns off the power transistor PTr1. That is, the power transistor PTr1is kept off.

When the abnormality disappears, the abnormality detection part DT1changes the detection result ER1 from high level to low level (at timet6). This causes the control part CT1 to again start outputting theoutput data VOUT from the reception circuit Rx1 unchecked. Because theoutput data VOUT is at the low level, the gate control signal OUT alsobecomes low, which keeps the power transistor PTr1 off (at time t6).

As explained above, the semiconductor integrated circuit 1 adopting thesignal transmission method of the third embodiment offers substantiallythe same effects as those of the first embodiment.

Fourth Embodiment

FIG. 44 shows a typical configuration of a semiconductor integratedcircuit 2 as the fourth embodiment of the present invention. Comparedwith the semiconductor integrated circuit 1 shown in FIG. 1, thesemiconductor integrated circuit 2 in FIG. 44 has an abnormalitydetection part DT2 and a control part CT2 which are formed over thesemiconductor chip CHIT and which replace the abnormality detection partDT1 and control part CT1, respectively, formed over the semiconductorchip CHP1. That is, the abnormality detection part and control part areprovided over the chip on the side of the transmission circuit Tx1. Theensuing paragraphs will mainly explain the configurations and operationsof the abnormality detection part DT2 and control part CT2.

The abnormality detection part DT2 has substantially the same circuitconfiguration as the abnormality detection part DT1. The abnormalitydetection part DT2 detects an abnormality that can cause a malfunctionin signal transmission via the isolation element ISO1 and outputs adetection result ER2 upon such detection. For example, upon detecting anabnormality, the abnormality detection part DT2 outputs a high-leveldetection result ER2; when not detecting any abnormality, theabnormality detection part DT2 outputs a low-level detection result ER2.The abnormality detection part DT2 includes a magnetic field changedetection circuit 201, a pulse width detection circuit 202, and a commonmode noise detection circuit 203, not shown.

The control part CT2 has substantially the same circuit configuration asthe control part CT1. When the abnormality detection part DT2 detects anabnormality, the control part CT2 outputs a stop signal to turn off thepower transistor PTr1 regardless of externally supplied transmissiondata VIN.

For example, when the detection result ER2 from the abnormalitydetection part DT2 is at the low level, i.e., when any abnormality thatcan cause a malfunction in signal transmission via the isolation elementISO1 is not detected, the control part CT2 outputs the externallysupplied transmission data VIN unchecked to the transmission circuitTx1. This allows the conduction state of the power transistor PTr1 to becontrolled in accordance with the transmission data VIN. On the otherhand, if the detection result ER2 from the abnormality detection partDT2 is at the high level, i.e., if an abnormality that can cause amalfunction in signal transmission via the isolation element ISO1 isdetected, the control part CT2 outputs a low-level stop signal to thetransmission circuit Tx1 regardless of the externally suppliedtransmission data VIN. This causes the transmission circuit Tx1 toconvert the low-level stop signal to the transmission signal and tooutput the signal. The transmission signal from the transmission circuitTx1 is forwarded to the reception circuit Rx1 as the reception signalvia the isolation element ISO1. Consequently the power transistor PTr1is controlled to be turned off.

What follows are explanations of specific configurations and operationsof the detection circuits included in the abnormality detection partDT2.

(Magnetic Field Change Detection Circuit 201)

The configuration and operations of the magnetic field change detectioncircuit 201 are substantially the same as those of the magnetic fieldchange detection circuit 101 and thus will not be discussed further.

(Pulse Width Detection Circuit 202)

The pulse width detection circuit 202 is a circuit that detects whetherthe interval between logical value changes in the transmission data VINsupplied from another semiconductor chip has become longer than apredetermined interval. In other words, the pulse width detectioncircuit 202 detects whether the pulse width of the PWM-modulatedtransmission data VIN fed from another semiconductor chip has becomegreater than a predetermined width. The remaining details of theconfiguration and operations of the pulse width detection circuit 202are the same as those of the pulse width detection circuit 102 and thuswill not be discussed further.

(Common Mode Noise Detection Circuit 203)

The common mode noise detection circuit 203 is a circuit that detectswhether common mode noise has exceeded a predetermined threshold range.In the common mode noise detection circuit 103 a in FIG. 16, thecomparator 1040 was shown furnished on the side of the other electrode(second power source side) of the capacitor 1037. On the other hand, inthe common mode noise detection circuit 203 in FIG. 45, the comparator1040 is shown provided on the side of one electrode (first power sourceside) of the capacitor 1037. The remaining details of the configurationand operations of the common mode noise detection circuit 203 are thesame as those of the common mode noise detection circuit 103 a and thuswill not be discussed further.

The abnormality detection part DT2 may be configured differently in sucha manner that, as a circuit for detecting an abnormality that can causea malfunction in signal transmission via the isolation element ISO1, thepart DT2 may include a power-on reset circuit 205, a low-voltagedetection circuit 206, a power source noise detection circuit 207, andan overheat detection circuit 209 in addition to the above-mentionedthree detection circuits. The power-on reset circuit 205, low-voltagedetection circuit 206, power source noise detection circuit 207, andoverheat detection circuit 209 correspond to the power-on reset circuit105, low-voltage detection circuit 106, power source noise detectioncircuit 107, and overheat detection circuit 109, respectively.

(Power-on Reset Circuit 205)

The power-on reset circuit 205 is a circuit that detects a predeterminedtime period over which the source voltage VDD0 on the side of thesemiconductor chip CHP0 stabilizes after power-on. The remaining detailsof the configuration and operations of the power-on reset circuit 205are the same as those of the power-on reset circuit 105 and thus willnot be discussed further.

(Low-Voltage Detection Circuit 206)

The low-voltage detection circuit 206 is a circuit that detects whetherthe voltage level of the source voltage VDD0 on the side of thesemiconductor chip CHP0 has become lower than a predetermined thresholdvalue. The remaining details of the configuration and operations of thelow-voltage detection circuit 206 are the same as those of thelow-voltage detection circuit 106 and thus will not be discussedfurther.

(Power Source Noise Detection Circuit 207)

The power source noise detection circuit 207 is a circuit that detectswhether the noise of the source voltage VDD0 on the side of thesemiconductor chip CHP0 has exceeded a predetermined threshold range.The remaining details of the configuration and operations of the powersource noise detection circuit 207 are the same as those of the powersource noise detection circuit 107 and thus will not be discussedfurther.

(Overheat Detection Circuit 209)

The overheat detection circuit 209 is a circuit that detects whether thetemperature inside or around the semiconductor chip CHP0 has becomehigher than a predetermined threshold temperature. The remaining detailsof the configuration and operations of the overheat detection circuit209 are the same as those of the overheat detection circuit 109 and thuswill not be discussed further.

As explained above, upon detection of an abnormality that can cause amalfunction in signal transmission via the isolation element ISO1 on theside of the semiconductor chip CHP0, the semiconductor integratedcircuit 2 of the fourth embodiment turns off the power transistor PTr1that is the target to be controlled. The inventive semiconductorintegrated circuit 2 thus prevents the power transistor PTr1 fromgetting inadvertently turned on and thereby forestalls the malfunctionof the load.

The foregoing paragraphs describing the fourth embodiment gave theexample in which the abnormality detection part DT2 outputs thedetection result ER2 solely to the control part CT2. Alternatively, theabnormality detection part DT2 may feed the detection result ER2 back toan external microcomputer. In this setup, upon detection of anabnormality by the abnormality detection part DT2, the microcomputer mayagain output the transmission data VIN of the same value. As anotheralternative, when the abnormality detection part DT2 detects anabnormality, the microcomputer may output as the transmission data VIN astop signal (low-level signal) that turns off the power transistor PTr1.

Also, the foregoing paragraphs describing the fourth embodiment gave theexample in which the semiconductor integrated circuit 2 has theabnormality detection part DT2 and control part CT2 furnished on theside of the semiconductor chip CHP0. Alternatively, as shown in FIG. 46,the semiconductor integrated circuit 2 may be configured differently insuch a manner that the abnormality detection part DT1 and control partCT1 are further provided on the side of the semiconductor chip CHP1.FIG. 47 is a timing chart showing typical operations of thesemiconductor integrated circuit 2 in FIG. 46. As is clear from FIG. 47,upon detection of an abnormality by the abnormality detection part DT1or DT2, the gate control signal OUT is controlled to be at the low level(i.e., the power transistor PTr1 is controlled to be off) regardless ofthe transmission data VIN.

Fifth Embodiment

FIG. 48 is a block diagram showing a typical configuration of asemiconductor integrated circuit 3 as the fifth embodiment of thepresent invention. The semiconductor integrated circuit 3 shown in FIG.48 includes a comparison part CMP1 that compares the logical value ofthe gate control signal OUT from the gate driver GD1 with the logicalvalue of the transmission data VIN corresponding to the gate controlsignal OUT in question. The comparison part CMP1 also functions as anabnormality detection part detecting an abnormality that can cause amalfunction in signal transmission via the isolation element ISO1. Thatis, if the logical value of the gate control signal OUT is differentfrom the logical value of the transmission data VIN corresponding to thegate control signal OUT, the comparison part CMP1 determines that anabnormality that may possibly cause a malfunction in signal transmissionvia the isolation element ISO1 has occurred.

Compared with the semiconductor integrated circuit 2 shown in FIG. 44,the semiconductor integrated circuit 3 in FIG. 48 has the comparisonpart CMP1 replacing the abnormality detection part DT2 and furtherincludes a transmission circuit (second transmission circuit) Tx2, areception circuit (second reception circuit) Rx2, and an isolationelement (second isolation element) ISO2. As mentioned above, thecomparison part CMP1 also serves as the abnormality detection part.

The transmission circuit Tx2 is formed along with the reception circuitRx1 over the semiconductor chip CHP1. The reception circuit Rx2 isformed together with the transmission circuit Tx1 over the semiconductorchip CHP0.

The transmission circuit Tx1 converts the gate control signal OUT fromthe gate drive GD1 into a pulse signal and outputs the pulse signal asthe transmission signal. The isolation element ISO2 forwards thetransmission signal coming from the transmission circuit Tx2 to thereception circuit Rx2 as the reception signal. Based on the receptionsignal from the isolation element ISO2, the reception circuit Rx2reproduces and outputs the gate control signal OUT.

The comparison part CMP1 compares the gate control signal OUT reproducedby the reception circuit Rx2 with the transmission data VIMcorresponding to the gate control signal OUT in question. If the logicalvalue of the reproduced gate control signal OUT matches the logicalvalue of the transmission data VIN corresponding to the gate controlsignal OUT, the comparison part CMP1 outputs a low-level comparisonresult; in case of a mismatch, the comparison part CMP1 outputs a highlevel comparison result.

Upon detection of an abnormality by the comparison part CMP1, thecontrol part CT2 outputs a stop signal to turn off the power transistorPTr1 regardless of the externally supplied transmission data VIN.

For example, if the comparison result from the comparison part CMP1 isat the low level, i.e., if any abnormality that can cause a malfunctionin signal transmission via the isolation element ISO1 is not detected,the control part CT2 outputs the externally supplied transmission dataVN unchecked to the transmission circuit Tx1. This allows the conductionstate of the power transistor PTr1 to be controlled in accordance withthe transmission data VIN. On the other hand, if the comparison resultfrom the comparison part CMP1 is at the high level, i.e., if anabnormality that can cause a malfunction in signal transmission via theisolation element ISO1 is detected, the control part CT2 outputs alow-level stop signal to the transmission circuit Tx1 regardless of theexternally supplied transmission data VIN. This causes the transmissioncircuit Tx1 to convert the low-level stop signal into the transmissionsignal that is output. The transmission signal from the transmissioncircuit Tx1 is forwarded via the isolation element ISO1 to the receptioncircuit Rx1 as the reception signal. Consequently the power transistorPTr1 is controlled to be turned off.

As explained above, upon detection of an abnormality that can cause amalfunction in signal transmission via the isolation element ISO1following the comparison between the gate control signal OUT and thetransmission data VIN, the semiconductor integrated circuit 2 as thefifth embodiment turns off the power transistor PTr1 that is the targetto be controlled. The inventive semiconductor integrated circuit 3 thusprevents the power transistor PTr1 from getting inadvertently turned onand thereby forestalls the malfunction of the load.

The foregoing paragraphs describing the fifth embodiment gave theexample in which the comparison part CMP1 outputs the result of thecomparison solely to the control part CT2. Alternatively, the comparisonpart CMP1 may feed the comparison result back to a microcomputer (notshown in FIG. 48). In this case, upon detection of an abnormality by thecomparison part CMP1, the microcomputer may again output thetransmission data VIN of the same value. As another alternative, if thecomparison part CMP1 detects an abnormality, the microcomputer mayoutput as the transmission data VIN a stop signal (low-level signal)that turns off the power transistor PTr1.

Also, the foregoing paragraphs describing the fifth embodiment gave theexample in which the semiconductor integrated circuit 3 has thecomparison part CMP1 and control part CT2 furnished on the side of thesemiconductor chip CHP0. Alternatively, the semiconductor integratedcircuit 3 may be configured differently in such a manner that theabnormality detection part DT2 is further provided on the side of thesemiconductor chip CHP0. As another alternative, the semiconductorintegrated circuit 3 may be configured in such a manner that theabnormality detection part DT1 and control part CT1 are further providedon the side of the semiconductor chip CHP1. Since the comparison partCMP1 also functions as the abnormality detection part, the comparisonpart CMP1 may be included in the abnormality detection part DT2.

Sixth Embodiment

Explained below as the sixth embodiment of the present invention is anapplication example of the semiconductor integrated circuit embodyingthis invention. A semiconductor integrated circuit 4 shown in FIG. 49 asthe sixth embodiment has the capability of detecting an abnormalityregarding the semiconductor chip CHP0 or CHP1 and turning off the powertransistor PTr1 upon such detection, as well as the capability offeeding the result of the detection from the abnormality detection partback to a microcomputer.

The semiconductor integrated circuit 4 shown in FIG. 49 has theabnormality detection part DT1 and control part CT1 furnished on theside of the semiconductor chip CHP1 and the abnormality detection partDT2 and control part CT2 provided on the side of the semiconductor chipCHP0. The basic configurations and operations of the functional blocksmaking up the semiconductor integrated circuit 4 are the same as thosediscussed so far. Thus some characteristic features of the componentsinvolved are mainly described below.

The abnormality detection part DT1 further includes a level detectioncircuit that detects the voltage level of the gate control signal OUT.The abnormality detection part DT1 has an encoder in place of the ORcircuit in its output stage. The abnormality detection part DT1 outputsthe detection result ER1 from the encoder to the control part CT1 andalso feeds the detection result ER1 back to the abnormal detection partDT2.

The abnormality detection part DT2 further includes the comparison partCMP1 as one of a plurality of detection circuits for detectingabnormalities. The comparison part CMP1 compares the detection resultstemming from the level detection circuit (logical value of the gatecontrol circuit OUT) and fed back from the abnormality detection partDT1 with the logical value of the corresponding transmission data VIN,and outputs the result of the comparison. The abnormality detection partDT2 has an encoder in place of the OR circuit in its output stage. Basedon the detection result from any one of the multiple detection circuitsit possesses, the abnormality detection part DT2 generates the detectionresult ER2 that is output to the control part CT2. Also, the abnormalitydetection part DT2 feeds the detection result ER2 and the fed-backdetection result ER1 back to a microcomputer, not shown.

For example, upon detection of an abnormality by the abnormalitydetection part DT1 or DT2, the microcomputer may again output thetransmission data VIN of the same value. Alternatively, if theabnormality detection part DT1 or DT2 detects an abnormality, themicrocomputer may output as the transmission data VIN a stop signal(low-level signal) that turns off the power transistor PTr1.

Where a plurality of semiconductor integrated circuits 4 are provided,the encoders included in their respective abnormality detection partsmay be coupled in a chain so that the detection result ER2 from theencoder in the last stage of the chain may be fed back to themicrocomputer, as shown in FIG. 50.

Seventh Embodiment

FIG. 51 is a block diagram showing a typical configuration of asemiconductor integrated circuit 5 as the seventh embodiment of thepresent invention. The semiconductor integrated circuit 5 configured asthe seventh embodiment controls the conduction state of two powertransistors PTr1 and PTr2 that are the targets to be controlled.

The semiconductor integrated circuit 5 shown in FIG. 51 includes thetransmission circuit Tx1, another transmission circuit (thirdtransmission circuit) Tx3, another transmission circuit (fourthtransmission circuit) Tx4, the reception circuit Rx1, another receptioncircuit (third reception circuit) Rx3, another reception circuit (fourthreception circuit) Rx4, the isolation element ISO1, another isolationelement (third isolation element) ISO3, another isolation element ISO4(fourth isolation element), the control part CT1, and gate drivers GD1and GD2. The reception circuits Rx3 and Rx4 and the isolation elementsISO3 and ISO4 make up a single abnormality detection circuit fordetecting an abnormality that can cause a malfunction in signaltransmission via the isolation element ISO1. FIG. 51 shows the powertransistor PTr1 as the target to be controlled using the transmissiondata VIN1 (first data signal) reproduced by the reception circuit Rx1.FIG. 51 also shows the power transistor PTr2 as the target to becontrolled using the transmission data VIN2 (second data signal)reproduced by the reception circuit Rx3.

The power transistors PTr1 and PTr2 are coupled in series between thesource voltage terminal HVDD and a ground voltage terminal to which aground voltage GND is supplied (the terminal is called the groundvoltage terminal GND). The voltage of a node between the two powertransistors PTr1 and PTr2 is used as a load drive signal Vcm. The powertransistors PTr1 and PTr2 are turned on and off in complementaryfashion.

The transmission circuits Tx1 and Tx3 are formed over the semiconductorchip CHP0. The isolation elements ISO1 and ISO4, reception circuits Rx1and Rx4, control part CT1, and gate driver GD1 are formed over thesemiconductor chip CHP1. The isolation element ISO3, reception circuitRx3, transmission circuit Tx4, and gate driver GD2 are formed over asemiconductor chip (third semiconductor chip) CHP2. The semiconductorchip CHP2 is driven by a third power source (source voltage VDD2, groundvoltage GND2) belonging to a third power supply system.

The configurations and operations of the transmission circuit Tx3,isolation element ISO3, reception circuit Rx3, and gate driver GD2 aresubstantially the same as those of the transmission circuit Tx1,isolation element ISO1, reception circuit Rx1, and gate driver GD1,respectively. It should be noted that the transmission circuit Tx1 issupplied with the transmission data VIN1 and the transmission circuitTx3 with the transmission data VIN2. The reception circuit Rx1 outputsoutput data VOUT1 and the reception circuit Rx3 outputs output dataVOUT2. The gate driver GD1 controls the conduction state of the powertransistor PTr1 by driving the output data VOUT1. The gate driver GD2controls the conduction state of the power transistor PTr2 by drivingthe output data VOUT2.

The transmission circuit Tx4 converts the output data VOUT2 from thereception circuit Rx3 into a pulse signal that is output as thetransmission signal. The isolation element ISO4 forwards thetransmission signal coming from the transmission circuit Tx4 to thereception circuit Rx4 as the reception signal. In this manner, thetransmission signal from the transmission circuit Tx4 is sent via theisolation element ISO4 to the reception circuit Rx4 as the receptionsignal. Based on the reception signal, the reception circuit Rx4reproduces and outputs the output data VOUT2.

When the reproduced output data VOUT2 is at the low level, the controlpart CT1 outputs the output data VOUT unchecked. When the reproducedoutput data VOUT2 is at the high level, the control part CT1 outputs alow-level stop signal regardless of the output data VOUT1 (i.e.,regardless of the transmission data VIN1).

Explained below are typical operations performed by the semiconductorintegrated circuit 5 in FIG. 51 when turning off the power transistorPTr1 and turning on the power transistor PTr2. In this case, thetransmission circuit Tx1 is supplied with the low-level transmissiondata VIN1 and the transmission circuit Tx3 with the high-leveltransmission data VIN2.

Where any abnormality that can cause a malfunction in signaltransmission via the isolation element ISO1 has not occurred, thereception circuit Rx1 outputs the low-level output data VOUT1 becausethere is no malfunction in signal transmission via the isolation elementISO1. At this point, the reception circuit Rx3 outputs the high-leveloutput data VOUT2. This causes the power transistor PTr1 to be turnedoff and the power transistor PTr2 to be turned on. That is, the normalswitching operations are carried out.

On the other hand, if there has occurred an abnormality that can cause amalfunction in signal transmission via the isolation element ISO1 and ifthe malfunction has actually taken place in the signal transmitted viathe isolation element ISO1, the reception circuit Rx1 outputs thehigh-level output data VOUT1 that is different from the transmissiondata VIN1. At this point, the reception circuit Rx3 outputs thehigh-level output data VOUT2. If the transmission circuit Tx4, isolationelement ISO4, reception circuit Rx4, and control part CT1 were notprovided, the power transistors PTr1 and PTr2 would both be turned on.This would let through-currents flow through the power transistors PTr1and PTr2 and increase consumption current.

The problem outlined above is resolved by the semiconductor integratedcircuit 5 of the seventh embodiment using the transmission circuit Tx4,isolation element ISO4, reception circuit Rx4, and control part CT1incorporated therein. Since the power transistors PTr1 and PTr2 areturned on and off in complementary fashion, the output data VOUT1 shouldbe at the low level when the output data VOUT2 is at the high level.Thus if the output data VOUT1 is at the high level when the output dataVOUT2 is at the high level, there is a possibility that a malfunctionhas occurred in signal transmission via the isolation element ISO1. Inthis case, based on the output data VOUT1 and on the reproduced outputdata VOUT2, the control part CT1 determines that a malfunction that cancause a malfunction in signal transmission via the isolation elementISO1 has occurred, and outputs a low-level stop signal. This turns offthe power transistor PTr1 and prevents through-currents from flowingthrough the power transistors PTr1 and PTr2, thereby inhibiting theincrease in consumption current.

As explained above, the semiconductor integrated circuit 5 as theseventh embodiment compares the output data VOUT1 from one receptioncircuit Rx1 with the output data VOUT2 from another reception circuitRx3 to detect an abnormality that can cause a malfunction in signaltransmission via the isolation element ISO1, and performs control toturn off the power transistor PTr1 that is the target to be controlled.The semiconductor integrated circuit 5 as the seventh embodiment thusprevents the power transistor PTr1 from getting inadvertently turned on.This in turn inhibits the increase in consumption current attributableto through-currents flowing through the power transistors PTr1 and PTr2.

The seventh embodiment above was shown configured so that upon detectionof an abnormality that can cause a malfunction in signal transmissionvia the isolation element ISO1, the power transistor PTr1 as one targetto be controlled is forcibly turned off. Alternatively, the embodimentmay be configured in such a manner that upon detection of an abnormalitythat can cause a malfunction in signal transmission via the isolationelement ISO1, the power transistor PTr2 as another target to becontrolled is forcibly turned off. As another alternative, theseconfigurations may be combined.

Alternatively, the semiconductor integrated circuit 5 as the seventhembodiment may be configured to have the abnormality detection part DT1and control part CT1 included in the semiconductor chip CHP1. As anotheralternative, the semiconductor integrated circuit 5 of this embodimentmay be configured to have an abnormality detection part (correspondingto the abnormality detection part DT1 in FIG. 1) and a control part(corresponding to the control part CT1 in FIG. 1) included in thesemiconductor chip CHP2. As a further alternative, the semiconductorintegrated circuit 5 of this embodiment may be configured to have theabnormality detection part DT2 and control part CT2 included on the sideof the semiconductor chip CHP0.

(Typical Packaged States of the Semiconductor Integrated Circuit 5)

Explained below in reference to FIGS. 52 through 58 are some typicalpackaged states of the semiconductor integrated circuit 5 embodying thepresent invention. Unless otherwise specified, each of the packagedstates shown in FIGS. 52 through 58 is an example in which thetransformer is used as the isolation element. Some of these packagedstates to be discussed below utilize an AND circuit as the control partCT1.

In each of the packaged states shown in FIGS. 52 through 55, a singlepackage PKG1 carries semiconductor chips CHP0, CHP1, and CHP2 isolatedfrom one another and operating from a different power supply systemeach. As shown in FIGS. 52 through 55, the isolation element ISO1 may beformed in a manner overlying the semiconductor chip CHP1, overlying thesemiconductor chip CHP0, spanning the semiconductor chips CHP0 and CHP1,or overlying a separately furnished semiconductor chip CHP3 a. Theisolation element ISO3 may be formed in a manner overlying thesemiconductor chip CHP2, overlying the semiconductor chip CHP0, spanningthe semiconductor chips CHP0 and CHP2, or overlying the separatelyfurnished semiconductor chip CHP3 a. Likewise, the isolation elementISO4 may be formed in a manner overlying the semiconductor chip CHP1,overlying the semiconductor chip CHP2, spanning the semiconductor chipsCHP1 and CHP2, or overlying a separately furnished semiconductor chipCHP3 b.

The packaged states in FIGS. 52 through 55 are each an example in whichthe transmission circuit (e.g., transmission circuit Tx1) and thereception circuit (e.g., reception circuit Rx1) are formed overdifferent semiconductor chips (e.g., semiconductor chips CHP0 and CHP1)respectively. Alternatively, the transmission circuit and receptioncircuit may be formed over a single semiconductor chip (i.e., commonsemiconductor chip). In this case, the area in which the transmissioncircuit is located and the area in which the reception circuit ispositioned are isolated from each other by an isolation layer formedinside the semiconductor chip.

Also, the packaged states in FIGS. 52 through 55 are each an example inwhich the power transistors PTr1 and PTr2 are discrete elementsfurnished outside the package PKG1. Alternatively, as shown in FIG. 56,the power transistors PTr1 and PTr2 may be furnished within the packagePKG1.

Furthermore, the packaged states in FIGS. 52 through 55 are each anexample in which the gate driver GD1 on the high side and the gatedriver GD2 on the low side are furnished over a single package PKG1.Alternatively, as shown in FIGS. 57 and 58, the gate driver GD1 on thehigh side and the gate driver GD2 on the low side may be furnishedrespectively over packages PKG1 and PKG2 that are different from eachother. In this case, the packages PKG1 and PKG2 are provided withadditional external terminals for permitting communication between thetwo packages.

In the example of FIG. 57, semiconductor chips CHP0 a and CHP0 b operatefrom a common power source (first power source), and semiconductor chipsCHP2 a and CHP2 b operate from another common power source (third powersource). In the example of FIG. 58, the semiconductor chips CHP0 a andCHP0 b operate from one common power source (first power source), andsemiconductor chips CHP1 a and CHP1 b operate from another common powersource (second power source). FIG. 58 shows a typical packaged state inwhich upon detection of an abnormality that can cause a malfunction insignal transmission via the isolation element ISO3, the power transistorPTr2 is forcibly turned off.

The packaged states in FIGS. 52 through 58 are each an example in whichtransformers are used as the isolation elements ISO1, ISO3 and ISO4.Alternatively, the type of the isolation elements ISO1 and ISO3 may bedifferent from the type of the isolation element ISO4. For example, FIG.59 shows an example in which transformers are used as the isolationelements ISO1, ISO3 and ISO4, whereas FIG. 60 indicates an example inwhich transformers are used as the isolation elements ISO1 and ISO3 anda capacitor is utilized as the isolation element ISO4.

The winding direction of the coil (clockwise or counterclockwise) makingup the transformer may be changed from one isolation element to another.For example, if the isolation element ISO1 has the tendency to transmithigh-level data erroneously under the influence of external magneticfields, the isolation element ISO4 may have its coil adjusted in layoutand in winding direction so as to develop the tendency to transmithigh-level data. Given such adjustments, even if malfunctions do occurin signal transmission via both the isolation element ISO1 and theisolation element ISO4, the power transistor PTr1 is controlled to beturned off. This prevents through-currents from flowing through thepower transistors PTr1 and PTr2 and thereby inhibits the increase inconsumption current.

The above-mentioned adjustments can be applied not only to cases wheremalfunctions are caused by external magnetic fields but also to caseswhere common mode noise can trigger malfunctions. For example, if theisolation element ISO1 has the tendency to transmit high-level dataerroneously under the influence of common mode noise, the isolationelement ISO4 may likewise have its coil adjusted in layout and inwinding direction so as to manifest the tendency to transmit high-leveldata. Given these adjustments, if malfunctions occur in signaltransmission via both the isolation element ISO1 and the isolationelement ISO4, the power transistor PTr1 is controlled to be turned off.This prevents through-currents from flowing through the powertransistors PTr1 and PTr2 and thereby inhibits the increase inconsumption current.

Alternatively, the isolation element ISO4 may be configured to beaffected by common mode noise or by external magnetic fields moresensitively than the isolation element ISO1. This configuration permitstransmission of the high-level data via the isolation element ISO4 atearlier timing than the high-level data via the isolation element ISO1,as shown in FIG. 61. This controls the power transistor PTr1 to beforcibly turned off by the reproduced output data VOUT2 before gettinginadvertently turned on by the output data VOUT1 (reproducedtransmission data VIN). That in turn prevents through-currents fromflowing through the power transistors PTr1 and PTr2 and thereby inhibitsthe increase in consumption current.

Each of the semiconductor integrated circuits implemented as the firstthrough the seventh embodiments discussed above may be applied toinverter equipment that drives a monitor (load), as shown in FIG. 62 forexample. The inverter equipment shown in FIG. 62 has three gate driverson each of the high and the low sides. Based on PWM-modulatedtransmission data (e.g., UH, UL) output from a microcomputer, thisinverter equipment controls currents (e.g., IU) flowing through themotor in analog fashion (see FIG. 63).

For example, if the abnormality detection part (not shown in FIG. 62)detects an abnormality, information about the detected abnormality isfed back to the microcomputer. The microcomputer transmits theinformation about the detected abnormality to peripheral devices.Specifically, the microcomputer may illuminate a warning lamp or displaythe abnormality-related information on the display screen of a carnavigation system. On verifying the glowing warning lamp, the useroperating an attached console can give the microcomputer relevantinstructions to carrying out appropriate processes.

The semiconductor integrated circuit embodying the present invention mayalso be applied to a motor drive apparatus mounted on electric vehicles,two-wheeled electric vehicles or the like; to a drive apparatus fordriving the compressor or motor mounted on home electrical appliancessuch as air conditioners and refrigerators; to a power control apparatusfor high-power home electrical appliances such as microwave ovens and IHcookers; to a drive apparatus for DC and AC power sources; to dimmercontrols for lighting equipment, backlights and displays; to washingmachines, inverter-controlled florescent lamps, microwave ovens, IHcookers, vacuum cleaners, LED lights, uninterruptible power supplies(UPS), solar power generation systems, cogeneration systems, pumps,liquid crystal displays (for backlight control), and PDP; and toindustrial inverters, machine tools, robots, elevators, wind powergeneration systems, NAS cells, forklifts, gold carts, and fuel cells.

It should be understood that the present invention when embodied is notlimited to the above-described first through the seventh embodiments andthat various modifications, variations and alternatives may be made ofthis invention so far as they are within the spirit and scope thereof.For example, in the first through the seventh embodiments discussedabove, the target to be controlled was shown to be the power transistoror transistors (e.g., power transistor PTr1 in FIG. 1) for example.Alternatively, the target to be controlled may be the IGBT, power MOS,GaN FET, SiC FET, or the combination of any one of these elements with asnubber diode.

Also in the first through the seventh embodiments discussed above, thecontrol part CT1 was shown to be an AND circuit for example.Alternatively, the circuit configuration of the control part CT1 may bechanged as needed as long as the control part CT1 can turn off the powertransistor PTr1 upon detection of an abnormality by the abnormalitydetection part DT1. The same holds for other control parts (e.g.,control part CT2) having the same capabilities as those of the controlpart CT1.

Further in the first through the seventh embodiments discussed above,the abnormality detection part DT1 was shown to have three detectioncircuits (magnetic field change detection circuit 101, pulse widthdetection circuit 102, and common mode noise detection circuit 103) forexample. Alternatively, the abnormality detection part DT1 may possessat least one of these detection circuits. The same holds for otherabnormality detection parts (e.g., abnormality detection part DT2)having the same capabilities as those of the abnormality detection partDT1.

It should also be understood that the configuration examples of thedetection circuits included in the abnormality detection part DT1 areonly for illustration purposes and may be replaced with otherconfigurations offering substantially the same capabilities.

Thus the scope of the invention should be determined by the appendedclaims and their legal equivalents, rather than by the examples given.

What is claimed is:
 1. A semiconductor integrated circuit comprising: afirst transmission circuit generating and outputting a firsttransmission signal reflecting a first data signal supplied fromoutside; a first reception circuit reproducing the first data signalbased on a first reception signal; a first isolation element isolatingthe first transmission circuit from the first reception circuit andtransmitting the first transmission signal as the first receptionsignal; a second transmission circuit generating and outputting a secondtransmission signal reflecting a second data signal supplied fromoutside; a second reception circuit reproducing the second data signalbased on a second reception signal; a second isolation element isolatingthe second transmission circuit from the second reception circuit andtransmitting the second transmission signal as the second receptionsignal; a third transmission circuit generating and outputting a thirdtransmission signal reflecting the second data signal; a third receptioncircuit reproducing the second data signal based on a third receptionsignal; a third isolation element isolating the third transmissioncircuit from the third reception circuit and transmitting the thirdtransmission signal as the third reception signal; a control part whichoutputs a stop signal regardless of the first data signal supplied fromoutside to the first transmission circuit when the control part decidesthat both the first data signal reproduced by the first receptioncircuit and the second data signal reproduced by the third receptioncircuit are the same logical level signals; a first gate driveroutputting a first gate control signal based on the first data signalreproduced by the first reception circuit; and a second gate driveroutputting a second gate control signal based on the second data signalreproduced by the second reception circuit and the second gate controlsignal being used to control on/off operations of an output transistorfor controlling a current flowing through a load.
 2. The semiconductorintegrated circuit according to claim 1, wherein, upon detection of anabnormality, the control part turns off the output transistor byoutputting the stop signal.
 3. The semiconductor integrated circuitaccording to claim 1, wherein the first, the second and the thirdisolation elements are comprised of a transformer.
 4. The semiconductorintegrated circuit according to claim 1, wherein the first, the secondand the third isolation elements are comprised of a GMR (Giant MagnetoResistive) element isolator.
 5. The semiconductor integrated circuitaccording to claim 1, wherein the first, the second and the thirdisolation elements are comprised of a capacitor.
 6. The semiconductorintegrated circuit according to claim 1, wherein the first, the secondand the third isolation elements are comprised of a photo-coupler. 7.The semiconductor integrated circuit according to claim 1, wherein thefirst and the second transmission circuits are mounted over a firstsemiconductor chip driven by a first power source, wherein the first andthe third reception circuits are mounted over a second semiconductorchip driven by a second power source, wherein the second receptioncircuit and the third transmission circuit are mounted over a thirdsemiconductor chip driven by a third power source and wherein thecontrol part is mounted over the second semiconductor chip along withthe first and the third reception circuit.
 8. The semiconductorintegrated circuit according to claim 1, wherein, upon detection of anabnormality, the control part turns off an output transistor byoutputting the stop signal.
 9. The semiconductor integrated circuitaccording to claim 1, wherein upon detection of an abnormality, thecontrol part outputs a stop signal regardless of the first data signalsupplied from outside to the first transmission circuit when the controlpart decides that both the first data signal reproduced by the firstreception circuit and the second data signal reproduced by the thirdreception circuit are the same logical level signals.
 10. A method ofsemiconductor integrated circuit, the method comprising: generating andoutputting, by a first transmission circuit, a first transmission signalreflecting a first data signal supplied from outside; reproducing, by afirst reception circuit, the first data signal based on a firstreception signal; isolating, by a first isolation element, the firsttransmission circuit from the first reception circuit and transmittingthe first transmission signal as the first reception signal; generatingand outputting, by a second transmission circuit, a second transmissionsignal reflecting a second data signal supplied from outside;reproducing, by a second reception circuit, the second data signal basedon a second reception signal; isolating, by a second isolation element,the second transmission circuit from the second reception circuit andtransmitting the second transmission signal as the second receptionsignal; generating and outputting, by a third transmission circuit, athird transmission signal reflecting the second data signal;reproducing, by a third reception circuit, the second data signal basedon a third reception signal; isolating, by a third isolation element,the third transmission circuit from the third reception circuit andtransmitting the third transmission signal as the third receptionsignal; outputting, by a control part, a stop signal regardless of thefirst data signal supplied from outside to the first transmissioncircuit when the control part decides that both the first data signalreproduced by the first reception circuit and the second data signalreproduced by the third reception circuit are the same logical levelsignals; outputting, by a first gate driver, a first gate control signalbased on the first data signal reproduced by the first receptioncircuit; and outputting, by a second gate driver, a second gate controlsignal based on the second data signal reproduced by the secondreception circuit and the second gate control signal being used tocontrol on/off operations of an output transistor for controlling acurrent flowing through a load.
 11. The method according to claim 10,wherein, upon detection of an abnormality, the control part turns offthe output transistor by outputting the stop signal.
 12. The methodaccording to claim 10, wherein, upon detection of an abnormality, thecontrol part turns off an output transistor by outputting the stopsignal.
 13. The method according to claim 10, wherein upon detection ofan abnormality, the control part outputs a stop signal regardless of thefirst data signal supplied from outside to the first transmissioncircuit when the control part decides that both the first data signalreproduced by the first reception circuit and the second data signalreproduced by the third reception circuit are the same logical levelsignals.
 14. The method according to claim 10, wherein the first, thesecond and the third isolation elements are comprised of at least one ofa transformer, a GMR (Giant Magneto Resistive) element isolator, acapacitor, and a photo-coupler.
 15. The method according to claim 10,wherein the first and the second transmission circuits are mounted overa first semiconductor chip driven by a first power source, wherein thefirst and the third reception circuits are mounted over a secondsemiconductor chip driven by a second power source, wherein the secondreception circuit and the third transmission circuit are mounted over athird semiconductor chip driven by a third power source and wherein thecontrol part is mounted over the second semiconductor chip along withthe first and the third reception circuit.
 16. A semiconductor circuitcomprising: at least three transmission circuits generating andoutputting first transmission signals reflecting data signals suppliedfrom outside; at least three reception circuit reproducing the datasignals based on reception signals; at least three isolation elementsisolating each of the at least three transmission circuits from the atleast three reception circuits and transmitting the transmission signalsas the reception signals; a control part which outputs a stop signalregardless of the data signals supplied from outside to one of the atleast three transmission circuits when the control part decides thatboth the data signals reproduced by one of the at least three receptioncircuits and another one of the data signals reproduced by another oneof the at least three reception circuits are the same logical levelsignals; a first gate driver outputting a first gate control signalbased on one of the data signals reproduced by one of the receptioncircuits; and a second gate driver outputting a second gate controlsignal based on a second one of the data signals reproduced by a secondone of the reception circuits and the second gate control signal beingused to control on/off operations of an output transistor forcontrolling a current flowing through a load.
 17. The semiconductorcircuit according to claim 16, wherein upon detection of an abnormality,the control part outputs a stop signal regardless of the data signalssupplied from the outside.
 18. The semiconductor circuit according toclaim 16, wherein the at least three isolation elements are comprised ofat least one of a transformer, a GMR (Giant Magneto Resistive) elementisolator, a capacitor, and a photo-coupler.
 19. The semiconductorcircuit according to claim 16, further comprising an abnormalitydetection part that detects a fault in a signal transmission via the oneof the at least three isolation elements.